SPECIAL ISSUE
Optimized extraction of dimension stone blocks
S. Mosch • D. Nikolayew • O. Ewiak •
S. Siegesmund
Received: 5 July 2010 / Accepted: 29 October 2010 / Published online: 30 November 2010
 The Author(s) 2010. This article is published with open access at Springerlink.com
Abstract The profitable production of dimension stone
mainly depends on the extractable block size. The regu-
larity and volume of the blocks are of critical importance,
and are controlled by the three-dimensional pattern of the
discontinuity system. Therefore, optimization of block size
has to be the aim when quarrying for natural stone. This is
mainly connected to the quantification of joints and frac-
tures, i.e., their spacing and orientation. The problem of
finding unfractured blocks within arbitrarily oriented and
distributed planes can be solved effectively by a numerical
algorithm. The main effects of joint orientations on block
sizes and shapes will be presented in this article. Quanti-
fication of unfractured blocks with the aim of optimization
is illustrated by detailed studies on several quarries. The
algorithm used in this study can be applied as a powerful
tool in the planning of a quarry and the future exploitation
of dimension stone. Application of the described approach is
demonstrated on practical examples of quarrying natural
stones, namely, sandstone, granite, rhyolite, etc. Block quar-
rying can be optimized by using the new 3D-BlockExpert
approach. The quantification of unfractured rock masses is
also shown to contribute to a more ecological protection and
the sustainable use of natural resources.
Keywords Production of dimension stones  Joints and
fractures  Block sizes  Optimization
Introduction
The term optimization implies improving a process that has
specifically defined goals. For this, it is necessary to con-
sider all the processes and modify them to achieve the best
possible results. The main factors which increase the
profitability of a dimension stone quarry are block size
optimization and the focus on high quality raw materials as
well as the avoidance of unnecessary waste and overbur-
den. In this context the volumes as well as the geometry
and the distribution of expected raw blocks is essential.
Initial prediction of the relative part sizes will help to
optimize the building stone production. Therefore, joints
and fractures are among the most important geological
structures, and its assessment is one of the most important
tasks during exploration and the ongoing quarrying
process.
The genesis of joint- and fracture-systems can be mul-
tifaceted and be traced back to orogenic, and epirogenic
processes, as well as shrinkage caused by cooling or des-
iccation. As a discontinuity in a deposit, all surfaces such
as faults, joints, cracks, fissures, or bedding planes has to
be taken into account. The formation of separated indi-
vidual blocks in a compact rock, the so-called in situ blocks
(Lu and Latham 1999), is linked to the intersection of these
discontinuities. Intrinsic structure characteristics such as
quartz- or calcite-veins are also considered, if it can be
foreseen that these vein tracings will open during further
processing. Furthermore, the discontinuity system might
impair the quality of a raw block even with mineralized
fissures, since the individual de´cor of a rock can be
interrupted.
Both the orientation and the respective distances of
discontinuities have a significant influence on the pro-
spective shapes and volumes of primary blocks. In general,
S. Mosch (&)  O. Ewiak  S. Siegesmund
Department of Structural Geology and Geodynamics,
Geoscience Center of the University of Go¨ttingen,
Go¨ttingen, Germany
e-mail: stephan.mosch@pigadi.com
D. Nikolayew
Frank Laboratory of Neutron Physics, Joint Institute
for Nuclear Research, Dubna, Moscow, Russia
123
Environ Earth Sci (2011) 63:1911–1924
DOI 10.1007/s12665-010-0825-7
wider distances result in large-sized blocks, if the orien-
tation of discontinuities does not diverge decisively from
orthogonality. When the geologic or tectonic situation
results in acute and irregular blocks, a more cost-intensive
and time-consuming process occurs, since these blocks
must be resized to manageable dimensions for processing.
If only one or more parameters, distances or dip angles are
varying intensely, the extracted material can be utilized for
low-value goods like gravel or paving stones (see Smith
1999).
Quarried raw blocks must generally meet certain criteria
to fulfil the technical and economical requirements of a
modern cutting inventory. The best conditions prevail if the
raw block sizes range between 6 and 8 m3 (Primavori
1999). The maximum dimension of the blocks conforms to
the weight, when considering the safety issues of the
transport and the handling of blocks during further pro-
cessing. Minimum volumes for natural stone blocks
determined for export are around 1–6 m3, whereas standard
dimensions range between 2.0 9 1.0 9 0.5 and 3.0 9
2.0 9 1.0 m (United Nations 1976). The dimensions of a
raw block are also a significant factor for the processing
with respect to the de´cor of a stone. While the width is
finally responsible for the number of slabs that can be
obtained from a block, its height and the length deter-
mine the size of each of those slabs. In this context,
intensively decorated rocks that show e.g., folding, the
broad side of a raw block has to show the corresponding
de´cor.
In many deposits, however, ideal conditions do not
prevail, so that blocks must be formatted to a processing-
friendly geometry. A beneficial situation for dimensional
stone mining is, for example, when the fragmentation
into rectangular blocks is defined by a natural orthogonal
fracture system. But in many cases, deposits of natural
building stone are affected by a distinct variability of the
orientation of joints, leading to irregular, often acute-
angled blocks, whereby each block then needs individual
cutting. In the Finnish granite industry, for example,
the yield of sellable stone products ranges from 5 to
10% of the total volume of rock excavated (Prissang
et al. 2007).
The problem of mutually orthogonal fracture patterns
was considered by Weber et al. (2001) and Weber and
Lepper (2002). More recent articles (Koch-Moeck and
Germann 2007; Prissang et al. 2006, 2007) are also devoted
to this problem. However, there is no general analytical
solution, but for most three-dimensional cases an effective
numerical solution will be presented in this article. The
computer program 3D-BlockExpert developed in this study
models the three-dimensional fragmentation of a deposit,
based on the investigation of the tectonic elements, dip
angles, and dip directions.
Methodological background
Data acquisition
Exact data acquisition is essential, both for the exploration
of new deposits and the ongoing maintenance of active
quarries. Consequently, the analysis of a discontinuity
system in a deposit has to comprise the localization,
mapping and evaluation of joints, bedding planes, fault
zones, etc.
Data collection is based on different methods, which are
adapted to the individual quarry situation. For further
details of discontinuity analyses see e.g., Smith (1999),
Priest (1993), Hoffmann and Siegesmund (2007a, b), or
Mosch (2009). Furthermore, different geophysical methods
are available such as Georadar. But the various methods
usually require a higher technical and financial expendi-
ture. Therefore, the mapping of joint space intervals can be
done by making direct longitudinal measurements at the
outcrop or in the quarry. The orientation of the joint sur-
faces is generally taken with a field compass. The funda-
mental problem is the recognition of the correct surfaces,
where in some cases very fine crack structures only become
visible after surface wetting.
In an ideal situation, the mapping of the joint system
should be performed on vertical quarry walls. By the so-
called ‘‘window sampling’’ or ‘‘scanline sampling tech-
nique’’ (ISRM 1978; Priest 1993), measuring lines have to
be sited on the quarry wall in a vertical and horizontal
orientation, enabling the acquisition of two joint sets
(Fig. 1: wall 1, joint sets A, C). To create a complete
picture of the joint system, another measurement needs to
be taken at right angles to the previous wall (Fig. 1: wall 2,
joint set B). A clear restriction that can appear is the ter-
mination behavior of the joint. Joints, whose strike can be
Fig. 1 Representative sketch in an area designated for excavation
showing the vertical and horizontal measuring lines on two quarry
walls intersecting joint sets A, B, and C
1912 Environ Earth Sci (2011) 63:1911–1924
123
followed along a section of the wall, can disappear after a
few centimeters into the depth of the rock and completely
discontinue or change orientation. Thus, the ‘‘window
sampling’’ may either register too small or too large dis-
tances between the joints. For assessing the area of the rock
to be excavated, it may be useful to thoroughly clean the
rock body, so that the traces of the joints in the wall can
be followed. This would complete the overall three-
dimensional picture of the rock body under consideration
for excavation.
Representation and application possibilities
The use of isoline diagrams like Schmidt Nets to depict
data obtained from the mapping of discontinuities like
joints and joint sets in oriented space has proven to be a
valuable tool. Figure 2 shows the orientation of different
joint and fracture systems developed in the same quarry. In
Fig. 2c, two steep joint sets are visible whose strike
direction is almost perpendicular to each other. This joint
system results in an almost uniform dissection of the rock
body exhibiting relatively rectangular blocks. The fracture
system shown in Fig. 2d also exhibits a preferred orienta-
tion, but joints striking in an E–W direction exhibit a
stronger variation. Here a third joint system is developed
leading to a stronger dissection of the rock body. Overall
the quarry shows a considerable heterogeneous distribution
of joints, where some aspects show a stronger fragmenta-
tion of the rocks.
Evaluating the data by the use of histograms is a good
way of representing the frequency distributions of the
distances between joints (see Singewald 1992). Simulta-
neously, when taking the mean of the joint distances into
consideration, the volume calculation of a so-called aver-
age block (x  y  z ¼ V; Singewald 1992) is possible.
When making a general assessment of a deposit, this
parameter is especially applicable in the area of sedimen-
tary stratiform deposits. If the joint structure deviates from
an orthogonal geometry, or if one or more joint sets show a
pronounced scattering, then only estimations can be made
whether a specific domain in the quarry is suitable for the
excavation of raw blocks. The quarry section showing a
greater variation in the strike and dip of the joints exhibits a
tighter joint spacing (Fig. 2e, f). Thus, it is more suitable
for excavation of crushed rock. The tight joint system
becomes really evident when the spacing is measured along
a horizontal line. Along a measuring distance of 30 m, 60%
of the joint intervals are below 0.5 m. Consequently, a
complete inspection of the orientation and joint space
distribution is possible within the discontinuity structure,
and by evaluating the general degree of dissection in a rock
body make estimates for the excavation of stone blocks.
Fig. 2 Quarry sections of the
Lo¨beju¨ner Qtz-Porphyry
(Germany): a in-active
dimension stone quarry and
b active quarry for grit and
gravel. Density distribution
diagrams (c, d) depict the
orientation of joints leading to
the expected shapes of in situ
blocks (green and red line
equals the orientation of each
quarry wall). The distribution
of joint distances (e, f) shows
a stronger fragmentation in
the quarry for grit and gravel
Environ Earth Sci (2011) 63:1911–1924 1913
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The software 3D-BlockExpert
To visualize the fragmentation of a rock body due to its
segmentation by discontinuities, the software known as
3D-BlockExpert has been developed (Nikolayew et al.
2007; Siegesmund et al. 2007; Mosch et al. 2009). The
computer program is able to evaluate data on the spatial
distribution of joints and provides information dealing with
the distribution of in situ blocks, as well as their volumes
and shapes. A joint is considered to be a plane, which can
be described mathematically with three points localized in
a coordinate system (Fig. 3). The necessary measurements
can easily be carried out in a quarry or in the early stage of
exploration, following the ‘‘window sampling’’ or ‘‘scan-
line sampling technique’’ (ISRM 1978; Priest 1993). The
software regards the treated area of a quarry as being a
parallelepiped, i.e., a geometric body composed of three
pairs of parallelograms, each pair in two parallel layers.
The body is divided into cells or voxels (volumetric pixel)
of the same size. Due to the integration of primary data into
this mathematical model, the description of its three-
dimensional segmentation is possible. An iterative process,
which is based on a numerical algorithm, assigns one color
to these voxels that build up one singular in situ block.
After the tessellation is modelled, the volumes of each
region can be easily calculated.
Based on this mathematical modelling, the software can
create two-dimensional sections parallel to each surface of
the treated rock body as a first step in evaluating a quarry
(Fig. 4). The number of sections for each direction depends
on the chosen number of voxels. Simultaneously, the voxel
size defines the resolution of the created model. Field
studies have shown that a resolution of 12 cm (edge length
of one voxel) is sufficient to describe natural joint or
fracture planes for the goal of dimension stone quarrying.
For practical purposes, it can be argued that this is a more
adequate description than in the case of a mathematical
object such as planes, which have zero volume. Moreover,
computing time is very closely connected to the size or
number of voxels under consideration. The time increases
as a cube to voxel edge length. So, for primary evaluation
and volume estimation in the field, a small number of
voxels is preferred.
Besides these two-dimensional sections the program
creates a data set, which can be translated into a three-
dimensional model. Moreover, with the software Intel
Array Viewer a multivariable modelling of the segmented
body with a free choice of section as well as a free rotation
of the whole model can be viewed in all directions of space
(Fig. 4). Thus, the user is able to examine the quarry sit-
uation from all possible perspectives, and also to get an
idea about the distribution of in situ blocks and to estimate
its shapes.
Fig. 3 Characteristic data input for the software 3D-BlockExpert for
describing joint planes using three points localized in a coordinate
system (after Mosch 2009)
Fig. 4 Possible outcomes for
3D-BlockExpert showing
two-dimensional sections
(middle) as well as three-
dimensional models
(right side) of a characteristic
block (compare with Fig. 3)
1914 Environ Earth Sci (2011) 63:1911–1924
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Results of modelling with 3D-BlockExpert
Field study: Lo¨beju¨ner Qtz-Porphyry, Rhyolite,
Germany
This example deals with the Lo¨beju¨ner Qtz-Porphyry,
a rhyolite body near Halle (Saale) in Saxony-Anhalt
(Germany). The rock mass is partly quarried for dimension
blocks. Generally, the quarry is characterized by a joint
system, which clearly shows visible changes in relatively
short distances (compare with Fig. 2). The variations
include orientation changes, varying numbers of joint sets,
and variations in spacing. The examined former quarrying
area is characterized by a joint system, which consists of
three main joint sets. The first set is comprised of (sub-)
horizontal joints cutting the rock at an average spacing of
0.52 ± 0.31 m. These planes usually are irregular or
undulating. The other two sets roughly strike NNE and
ESE. They are characterized by steep dipping planes,
which show a large continuity in parts but can also be
restricted to individual layers. The sets intersect each other
at roughly 90 and show an average spacing of
0.82 ± 0.54 m. The roughly orthogonal character of the
joint system causes more or less rectangular in situ block
shapes. However, the low spacing and high joint density
causes relatively small block volumes. Based on the
spacing distribution and the approach of Palmstro¨m (1995)
an average block volume of 0.4 m3 has been calculated.
The average joint density in the examined rock mass is as
high as 4.3 joints per m3 and thus, according to Sousa
(2010), too high for the exploitation of large volume
blocks.
For this reason, it is highly important to locate areas
with lower joint density, and thus higher block volumes.
For modelling the joint system with 3D-BlockExpert a
body of 7 9 6 9 4 m was chosen (Fig. 5). After data
acquisition in the field, the first steps were reconstructing
the joint pattern and defining the planes for the model input
file. The voxel size chosen for the model was 12.5 cm in
each direction, so one voxel corresponds to a volume of
roughly 2 dm3. The model comprises 20 joints, which were
partly constructed based on orientation measurements and
geometric extrapolation.
The resulting model shows a partly orthogonal character
of the joint system, although some joint planes show ori-
entation deviations (Fig. 6). For this reason, the modelled
rock mass comprises a small number of in situ blocks with
an acute-angled shape as well. Based on the model, the
average volume of the blocks is roughly 0.5 m3 after
removing the voxels attributed to joint planes and little
rock volumes \100 voxels, which matches the theoreti-
cally calculated average. The largest blocks in the mod-
elled rock mass have a volume [2 m3 and are located on
the SSW side of the rock mass. Summarizing, the relatively
small block volumes and the partly non-orthogonal
geometry, which would cause material losses during for-
matting of dimension blocks, disqualify the rock mass for
quarrying of large dimension blocks. Due to the low
spacing in all three joint sets, there is no way of optimizing
the yield in this case.
Field study: Bucher Sandstone, Germany
Massive sandstone deposits are characterized frequently by
a more or less orthogonal joint pattern. In some quarries the
joint system enables the extraction of orthogonal raw
blocks without using e.g., drilling machines or explosives.
For dimension stone purposes a more complicated situation
is given in the deposit of the fine- to medium-grained
Bucher Sandstone. Here the joint pattern is characterized
by at least two different sets of joints. One is clearly N–S
striking with dip angles of more than 80 (Fig. 7). These
steeply dipping joints are cut by a second set of joints,
which show a higher variability in both, first of all strike as
well as dip angle. In the actual quarry situation there was a
lack of subhorizontal joints. Only in the upper part one can
see single joints with estimated dip angles of around 10–
15. In total the rock body exhibits a heterogeneous
Fig. 5 a In-active quarry
section of the Lo¨beju¨ner Qtz-
Porphyry (rhyolite; Germany):
the joint pattern is characterized
by a more or less homogeneous
and orthogonal orientation of
joint sets (compare with Fig. 2).
b Two-dimensional front view
of the quarry section
in a modelled with
3D-BlockExpert
Environ Earth Sci (2011) 63:1911–1924 1915
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fragmentation, which leads to problems in the extraction
process.
In detail it becomes clear, that the actual wall of the
quarry does not really fit the orientation of the joint pattern,
which can be easily shown by using two-dimensional
sections modelled with 3D-BlockExpert. For this reason a
segment of the actual wall was determined in detail
(Fig. 8). Here, the traces of the drilling processes are
clearly visible showing an additional but avoidable frag-
mentation of the in situ blocks. The direction of the
excavation front must be changed to optimize the dimen-
sional stone to waste rock ratio.
The quarry was examined a second time. The general
joint pattern for a newly opened of the quarry is more or
less similar to the previous observation. The strike of the
main joints has rotated only a few degrees in an E–W
direction and the more heterogeneous sets of joints is less
distinct. Due to the removal of the sedimentary covering
(compare with Fig. 7), it was possible to collect data
concerning the joint distribution in all directions of space,
which could be brought together into a three-dimensional
model (Fig. 9). In connection with the two-dimensional
section of the expected quarry bottom, it becomes clear that
especially the southern part of the treated body exhibits a
Fig. 6 a Three-dimensional
model of the quarry section of
the Lo¨beju¨ner Qtz-Porphyry
shown in Fig. 5. b Due to the
multifaceted possibilities of
rotation and section choice, the
largest in situ block can be
detected in the lower right back
part of the treated rock mass
Fig. 7 Quarry of Bucher Sandstone (Germany): the joint analyses
show that an N–S striking and steep dipping system of joints is cut by
a more heterogeneous set of joints
Fig. 8 Quarry of Bucher Sandstone (Germany): modelled section of
a possible quarry bottom, which can be expected with an ongoing
extraction process. An additional fragmentation of in situ blocks is
clearly visible in detail due to the use of drilling machines. To fit the
quarry direction to the best possible joint pattern, a suitable rotation
should be carried out
1916 Environ Earth Sci (2011) 63:1911–1924
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strong and heterogeneous fragmentation. Moreover, this
part is also cross-cut by two distinct subhorizontal joints,
which were described above. However, the actual wall
mainly shows drilled surfaces. To summarize, the change
of the extraction front can lead to a greater exploitation of
raw blocks.
Modelling for optimization of final block cutting
Rock bodies that are essentially compact, homogeneous
and have widely spaced joints show similar possibilities for
optimization. This only occurs when a few discontinuities
like distinctly colored veins or similar irregular structures
are present. If these elements do not conform to the char-
acteristic rock ornamentation, a significant amount of
material loss can result, which may continue up to the
cutting of the raw block (Fig. 10).
Figure 11 shows a schematic representation of a quarry
that is pervaded by such bands. In this situation the
placement depth of the slab can have a positive impact on
the amount of waste material produced. The rotation cor-
responds to the longitudinal axis of the raw block. The
theoretically usable parts of the raw blocks are compared,
which is given by the bearing of the longitudinal axis at
right angles to the excavation direction (Fig. 11a), and
parallel to the excavation direction (Fig. 11b) for the fol-
lowing extraction steps. In the second case, the length of
the raw block is defined by the size of the extracted slab.
Hence, the maneuverability is the solely limiting factor for
the detached sections. To counteract this, a reduction in the
terrace height should be done.
At this point sections parallel to the extraction front can
be helpful. The respective sections are chosen in such a
way that the front and backside of the potential slab can be
rendered, where the thickness represents a dimension in the
final raw block. The form of the resulting in situ blocks can
be constructed from these simple geometric relationships,
whereby the primary rock waste can be estimated from the
Fig. 9 Quarry of Bucher
Sandstone (Germany):
characteristic three-dimensional
model of the upper section of
the quarry showing the
heterogeneous fragmentation of
the treated block in the southern
part. The two-dimensional
section of the expected quarry
bottom parallel to the actual
quarry wall explains the need
for changing the excavation
front
Fig. 10 Theoretical waste
material resulting from the
formatting and cutting of raw
blocks from a simple cleaved
slab
Environ Earth Sci (2011) 63:1911–1924 1917
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resulting perpendicular parting of the side surfaces. As a
consequence, it is possible to fill in the best surface area
utilization with regards to the actual usable material in two
dimensions.
In Fig. 12 such an optimization of formatting a raw
block is depicted. From a multitude of possibilities three
examples are singled out. However, it becomes clear that a
corresponding displacement of the arranged raw blocks as
well as the possible number can also influence the neces-
sary cutting work. Economic factors also have to be taken
into consideration. The highest block number can be real-
ized with arrangement possibility C. However, the for-
matting is connected to a very high labor input (relative
cutting length) in contrast to the arrangement possibility B.
In this case, the expected price segment of the rock has to
be taken into account, and the additional earnings have to
be balanced against the cost overruns for production.
Through a corresponding evaluation of successively
extracted slabs, additional prognostic information can be
obtained concerning the number and volume of raw blocks
in the excavating section. Besides the direct planning of
excavation, the process can be viewed as a tool, where for
example, further steps of manufacture are planned or the
requirements of the market can be aimed for. The pre-
requisite for such an optimal utilization is that the regarded
area is free of defects. Areas that show, for example, a clear
change in color or something similar have to be excluded,
especially when the stone does not meet the defined stan-
dards. One problem that can occur is when rock varieties
contain ornamentations defined by specific structural ele-
ments, and thus requires a particular orientation of the raw
block in the extracted slab.
Discussion
The goal in the excavation of dimension stones is to pro-
duce rectangular-shaped raw blocks for further use in the
stone industry. In many cases, it is not possible to extract
such corresponding blocks with the requisite perpendicu-
larity because of deviations in the joint system. This is why
a worldwide average of around 50% (Montani 2003)
overburden is produced from the excavation and formatting
of the in situ blocks. Frequently this value lies much
Fig. 11 Schematic
representation of a homogenous
and compact rock body that is
pervaded by a few irregular
discontinuities. Adjusting the
size of the extracted slabs and
the arrangement of the
recovered raw blocks can have a
positive effect on the quality of
the stone-waste material
balance. Different colors
designate the excavation
direction for the following
successive steps. Orientation of
the longitudinal side of the raw
block: a in the excavation
direction and b at right angles to
the excavation direction. The
fraction of completely usable
raw blocks is given in percent
1918 Environ Earth Sci (2011) 63:1911–1924
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higher, whereby the demand for the quality of a rock and
its marketability or rather its premium price segment takes
precedence. When removal rates of 80% or more occur in
excavating gray colored granites, for example, the profit-
ability of a deposit must be called into question.
The model in Fig. 13 shows in an exemplary way how
changes in a system of orthogonal discontinuities occur,
when accompanied by a rotation in one or both joint system
groups. A comparison of the joint spacing distribution
leads to the same results in all the three cases. Furthermore,
an increase in material loss occurs, and that a simultaneous
decrease in the average block size can be documented
(Mosch 2009). Excavating a dissected stone deposit in this
way leads to lower earnings, which has been demonstrated
by a comparative evaluation in magmatic deposits from
Thailand (Hoffmann and Siegesmund 2007a, b).
Stone deposits are a complex three-dimensional rock
body, and the model presented above deviates from a
natural example. This means that an orientation of the
joints, such as those illustrated in Fig. 13 may only be
aligned vertically with exception in some cases. Thus, a
further decrease in the production rate results, based upon
the angular deviation of the defined planes in an in situ
block.
The impact of the angular deviations described above
becomes very apparent in the Negro Grapesa qtz-bt diorite
quarry in Spain (Fig. 14a). The rose diagram (Fig. 14b)
shows a relatively heterogeneously strike distribution of
the joints. Two distinct preferred orientations can be dis-
tinguished that dissect each other at an angle between 60
and 70 (Fig. 14c). The excavation wall or floor of the
quarry only follows to a minor degree the general trend of
Fig. 12 Detection of large
volume in situ blocks and the
optimization of raw block
production (block size:
3 9 2 9 1.8 m) by utilizing the
model generated with data from
the joint system analysis in the
software 3D-BlockExpert. For
optimal surface area utilization
three examples from a large
number of possibilities are
presented (granite; San Antonio,
Sardinia)
Environ Earth Sci (2011) 63:1911–1924 1919
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the joints, which is probably due to the heterogeneity of
their distribution. Many parts of the quarry walls show
small and large scale outbursts at the corner intersections as
a result of this heterogeneity. Moreover, between the joint
planes and the cutting direction acute angles are observable
(Fig. 14d). As a consequence, the overburden contains
many acute-angled leftover pieces, which are produced by
the drilling of the in situ blocks (Fig. 14e). For block
excavation it is essential that stone deposits exhibit an
appropriate distribution of joints, when at least one
Fig. 13 Increase of cutting
(overburden) remains with
decreasing average block size
due to the joint system deviating
from orthogonality where the
spacing pattern remains equal.
The characteristic joint density
distributions depict the
orientations of each joint pattern
Fig. 14 Impact of a non-
orthogonal joint structure:
a quarry of commercial grade
Negro Grapesa (qtz-bt-diorite,
Spain), b excavation horizon
with accompanying joint
orientation rose diagram and
sketch depicting the measured
joints (black line) as well as the
wire-cut sections, c acute-
angled cutting of joints on the
excavating horizon, d executed
cut at an acute angle to the
NE–SW striking joint, and
e mine tailings with a large
number of non-rectangular
leftover blocks. See text for
explanation
1920 Environ Earth Sci (2011) 63:1911–1924
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direction of a natural joint surface in a rock can be utilized
for production.
Another aspect for dimension stone utilization is the
homogeneity of the joint surfaces and their distribution,
along with the distribution of the joint spaces and the
orientation of the discontinuities. Marbles or other meta-
morphic rock deposits are especially characterized by
heterogeneous joint. Figure 15 shows an example of the
joint distribution at the excavation wall in a quarry from
the Spanish marble province Macael (Mosch 2009). In this
quarry section, joints with two main strike directions are
recognized (Fig. 15b). The joint structure almost matches
the orientation of the quarry wall. However, the presence
of acute angularity is also a problem. Due to strong
fluctuations in the dips of the joints, the output for well-
dimensioned raw blocks with a specified form is consider-
ably diminished. The dips show a relatively even distribution
and cover a spectrum ranging from 5 to 88. The entire
NNE–SSW striking joint system shows a small variation in
the dip and must be placed somewhat steeper. Because of the
excavation wall orientation and the strong dip variation in
the joint sets that are hardly observable, an estimation of the
possible quarry output is strongly limited. In this case, an
additional wall parallel the NW–SE striking joint system
would have to be made accessible.
When considerable deviations occur in the orthogonal
structure or the joints show strongly fluctuating dip direc-
tions, applying histograms should be done with caution for
the assessment of the joint spacing distribution. Especially
in this case, the choice of the measuring line can have an
influence on the relative frequency distribution (Fig. 15a).
This can also result in deviations when calculating the
average volume of a block (Mosch 2009).
In general, the results from a discontinuity analysis may
show certain variations dependent on the lithology or the
tectonic conditions. In sandstones, for example, a phe-
nomenon that frequently occurs is a wave-like course of the
bedding, which results in strong changes in the bedding
thickness. Similar observations can be seen in the joints of
granitic rock bodies. Thus, caution is required when mak-
ing an assessment of the joint spacing distribution.
Through a heterogeneous formation of the joint struc-
ture, however, it becomes clear that a two-dimensional
section of a deposit has limited significance when it is
based solely on the distribution of joint spaces. Another
example where the complexity of the joint system and its
impact to the economical value of a deposit are clearly
visible is the quarry La Cantera Kinzigita in Argentina
(Fig. 16a, Mosch 2009). This quarry is dedicated to the
extraction of Azul Tango, a cdr-gt gneiss. When regarding
the fracture system, both the strike direction and dipping
angles of the joint and fracture planes show an obvious
variability. The density distribution of the orientation data
shows a preferred E–W strike direction and steeply dipping
joint planes (Fig. 16b). In spite of a larger variation in
strike, two main joint sets could be identified. These sets
intersect each other at angles between 60 and 70. The
spacing data display a closely spaced joint system with an
average spacing of about 1 m in all spatial directions
(Fig. 16c). Based on the joint spacing, an average block
volume of approximately 0.9 m3 has been calculated. From
all the data an extensive and unsteady joint and fracture
system has been deduced. The heterogeneous character of
the joint system finally led to the closing of the quarry.
Both exploitation and formatting of dimension blocks
has been achieved by the use of drillings and explosives.
The examination of several parts of the stopping levels
showed that the quarrying strategy has been poorly or even
not at all adjusted to the local geological conditions.
Without regarding the local joint system, the vertical
Fig. 15 a Sketch of the joint
system pattern on a quarry wall
(Blanco Macael, marble, Spain),
b diagrams depicting the joint
distribution in the above quarry,
and c joint space mapping along
various traverses (orange-
below, grey-above,
corresponding to the sketch in
a that result in different average
surface measurements. See text
for explanation
Environ Earth Sci (2011) 63:1911–1924 1921
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drillings broke through joint faces and possibly damaged
large-sized in situ blocks. Damages have been visible on
many raw dimension blocks in the stock. Defects ranged
from healed joints to open joint planes or grave deviations
from orthogonal geometries. In spite of this, the yield has
been about 10–20%.
The more reasonable way would have been a selective
exploitation concentrating on individual large volume
blocks. A basic prerequisite for this would have been the
recognition of the preferred joint orientation and the par-
allel adjustment of the exploitation faces to the main strike
direction (approximately 100–280). In addition, all faces
should have been cleared of waste to allow for a better
overview of the run of joints and fractures. Each quarrying
step should have been planned according to the charac-
teristics of the joint system, which requires a constant
detailed analysis of the joint and fracture system to locate
individual large volume blocks in the rock mass. These
blocks should be uncovered gently by using the existent
joints of the rock mass. Regarding the high quality and
value of the material, a higher amount of waste material
connected to the extraction of defect-free large volume
blocks could have been eventually acceptable.
Excavation of dimension stones can be achieved, how-
ever, when an ideal coordination of the mining procedure
takes the elements of the joint system structure into
account. This situation has been ideally implemented in the
Ba¨renburg Quarry (Switzerland) by the extraction of the
commercial grade Verde Andeer (Fig. 17). In this gneiss
complex, two main joint sets occur next to horizontally
aligned joints (joint set A), which are not represented in the
discontinuity analysis due to the distinct orientation and
equally spaced joint intervals. This is an ENE striking joint
system with some dips reaching greater than 80 (joint set
B), as well as being frequently healed by tourmaline
mineralization (Fig. 17b). Overall these healed joints are of
low stability, whereby potential joints can open during the
process of excavation. This healed joint system is cut along
strike by another approximately 90 joint set C, whose
average dip is about 50 to the NNW. Like the horizontal
joints, these joints exhibit a low mechanical coherence, and
can be detached by the use of a few drill holes at intervals
of around 1.5 m and the gentle application of well-placed
explosive charges. In general, this produces a joint struc-
ture in which two main joint sets are almost perpendicular
to each other (joint sets A and B), and a diagonal system
(joint set C) that cuts both.
The first step of an extraction is completed by the
placement of tightly spaced core holes, which are drilled
perpendicular to the diagonal joint. Only one layer is
drilled through. In the second step, joint set C will be pried
open along the mapped part of the quarry at a length of
around 40 m. At the same time the mineralized joints of
joint set B can open. The mining floor is defined by the
horizontal bedding joints (joint set B). This produces non-
rectangular formats in the in situ blocks, which then has a
part of the waste material removed creating a squaring of
the block. Based on the tectonic conditions in the Ba¨ren-
burg Quarry, this can not be avoided by a change in the
mining procedure.
Summary
The complexity of a joint system can clearly generate
problems concerning the opening of a quarry and defining
Fig. 16 a Quarry ‘‘La Cantera
Kinzigita’’ (Azul Tango,
cdr-gt-gneiss, Province of
Co´rdoba, Argentina). The
b orientation data and c the
spacing data depict a closely
spaced joint system without a
preferred orientation
1922 Environ Earth Sci (2011) 63:1911–1924
123
the direction of ongoing mining (Primavori 1999). Hence,
the new approach to characterize and quantify unfractured
rock masses for optimization of its use for dimension stone
production is an outstanding method for the processing of
joints in all spatial orientations. And furthermore, as a
means for depicting two- and three-dimensional represen-
tations of a dissected rock body, which is based upon
detailed mapping of the discontinuity system. The respec-
tive volume of the in situ blocks can be calculated simul-
taneously with the modelling of the stone deposit as well as
estimating the resulting geometries. The best possible
course for the quarrying is when the extraction is aligned
with the joints, so that unnecessary cuts do not cause a
further dissection of the rock body. Thus, it is possible to
detect areas that are not minable, whereby greater amounts
of waste material can be avoided.
In terms of profitability of a dimension stone quarry, the
arrangement at the extraction wall is of importance for
directly adapting the planning steps at the running excava-
tion site. This is significant for the slab thickness or the
quarry wall height, which is dependent on the given geo-
logical as well as tectonic relationships in a deposit. Using
the natural breakage of the stone lowers the time-consuming
and cost-intensive process of splitting the stone by drilling or
saw cutting. Even this aspect can be achieved with the new
approach by using the software 3D-BlockExpert when
considering the possible extraction variations. The so-called
differential view of the two sections describes the spatial
construction of a potential slab as seen in a two-dimensional
representation. Cutting planes with a specific spacing are
chosen that describe the front and back of the extracted slab,
which are made to match the final dimensions of the raw
block. The actual exploitable material can be quantified by
the removal of the overburden when drilling perpendicular to
the wedge faces. Afterward the remaining quality stone can
be filled out (in two dimensions) with respect to the best
computer-assisted surface exploitation. In the optimization
example, three excellent cases are singled out from a wide
variety of possibilities. However, a dislocation in the
arrangement of the blocks can clearly influence the possible
number of raw blocks as well as the necessary cutting work.
At the same time careful consideration has to be given to the
economic factors. The highest block number can be realized
by arrangement C, however, the formatting is connected to a
higher labor input (cutting length). In such a case the con-
sideration between more production costs and possible
increased profits is mandatory. By evaluating the succession
of extracted slabs, additional predictions can be made in
regards to the number and volume of raw blocks that can be
produced in future locations from the quarry. With the
support of the actual excavation plan a tool can be devel-
oped, whereby further steps in the manufacturing process are
planned, or selective extraction is done in reaction to the
needs of the market.
In summary, a systematic and detailed map of the joint
structure in a quarry enables one to:
• estimate the possible uses of the stone deposit
• detect areas which are not suitable for use and
concentrate on areas where high quality resources occur
• optimize and adapt the extraction process
• and optimize the formatting process of the raw blocks.
By paying attention to the spacing distribution and the
orientation of the joints that occur one can:
Fig. 17 Quarrying of the Verde
Andeer Orthogneiss
(Switzerland): a joint
distribution in the eastern part of
the Ba¨renburg Quarry (Toscano
AG) and b joints healed by
tourmaline mineralization
acting as potential fractures. See
text for further information
Environ Earth Sci (2011) 63:1911–1924 1923
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• achieve a positive influence between the relationship of
the overburden to the usable stone
• optimize the block exploitation, and thus, positively
influence the profitability of the quarry
• and increase the effective production and utilization of
the natural stone resources.
In addition to the economic components, unnecessary
environmental damages that accompany an uncontrolled
exploitation or the effects of expanding the quarry can be
avoided. Therefore, a contribution can be made toward
ecological protection and the sustainable use of natural
resources.
Open Access This article is distributed under the terms of the
Creative Commons Attribution Noncommercial License which per-
mits any noncommercial use, distribution, and reproduction in any
medium, provided the original author(s) and source are credited.
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