Marble - Colorado Geological Survey

quarries, may be nothing more than planes of
weakness or may be well developed, open
cracks. Joint spacing is variable, ranging from
tens of feet down to inches. Uniform, wide spacing
of parallel joints can add to the value of a
deposit as production costs will be decreased as
waste may be minimized by running cut walls
parallel with the major joint system.
Joints were mapped within the project area
to obtain the prevalent direction and orientation
for quarry planning. Most of the major joints
were oriented vertically in the old quarry area
and have an easterly strike. The verticality is
an advantage but the easterly strike requires
that the blocks will be oriented at an angle to
the strike of the outcrop and hillside. Joints to
the south in the outcrops of white marble are
random and more prevalent. Experts in the
field and CGS's examination of the Yule Quarry
indicate that jointing decreases with distance
from surface weathering. However, there are
beds of marble that are so severely jointed that
no blocks could be successfully quarried.
Specifically, these areas include the white beds
above the previously quarried marble, and the
upper beds along the south property line.
Soundness is also a function of mineral constituents
and texture when considering the
competence of marble when slabbed. Variable
cohesion between non-uniform size and type of
mineral grains can place restrictions on product
use or may require slabs to be reinforced.
Open voids, veins, or flow structures can also
decrease the competence of marble when slabbed.
Based on knowledge gained through years
of practical experience, marble has been universally
classified into four groups based on
characteristics encountered upon fabrication.
The system indicates required fabrication techniques
which are considered necessary, as based
on standard trade practice (MIA, 1987):
Group A: Sound marbles and stones, with
uniform and favorable working qualities.
Group B: Marbles and stones similar in
character to the preceding group, but with
working qualities somewhat less favorable; may
have natural faults; a limited amount of waxing
and sticking necessary.
Group C: Marbles and stones with some
variation in working qualities; geologic flaws,
voids, veins, and lines of separation are common;
it is standard practice to repair these variations
by sticking, waxing, and filling; liners
and other forms of reinforcement employed
when necessary.
Group Ds Marbles and stones similar to the
preceding group, but containing a larger portion
of natural faults, and a maximum variaion in
working qualities; requires more of the afore
mentioned finishing techniques. This group comprises
many of highly colored marbles prized
for their decorative qualities.(After MIA, 1985)
Colorado-Highland marbles generally fall
into Group B. Polished slabs are fairly competent
except for a few scattered grains which may
spall out during finishing. All material collected
and finished is from the weathered zone of
the deposit. Soundness and polishability are
expected to increase with depth.
All of the above mentioned characteristics of
a building stone can affect market value. It is
the aesthetic qualities of polishability and general
attractiveness though which will ultimately
place a particular stone in high demand.
Engineering Constraints of Marble
Modern building design and construction requires
increased knowledge of the physical
limitations of building materials. As performance
requirements become more demanding, so
does increased need for quantitative data on
construction materials. The Natural Building
Stone Committee of the American Society for
Testing and Materials (ASTM) has established
standards for the testing and documentation of
the physical properties of marble. The recommended
tests are:
C97 Absorption and Specific gravity
C99 Modulus of Rupture
C170 Compressive Strength
C241 Abrasion Resistance
C880 Flexural Strength
Standard specifications for marble building
stone (exterior), and descriptions of test methods
from the Annual Book of ASTM Standards
are referenced at the end of this report. It
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