Marble - Colorado Geological Survey

should be noted here that the results of these
tests will not necessarily determine the relative
value of a marble, but do give insight into its
general use.
Gray marble from the old Colorado-Highland
quarry was tested by the Indiana Geological
Survey for all of the above mentioned ASTM
tests except flexural Strength (C880). Test report
forms submitted to CGS by IGS are reprinted
in Appendix C. To avoid the problem of
running tests on severely weathered product,
fairly large blocks were submitted enabling IGS
to obtain relatively fresh marble from below the
weathering rind. All tests were run in two phases.
Material from the exterior portion of blocks
was cut and tested initially. Less weathered
material from the interior portions of the samples
was subsequently run to check initial
results. Weathering of blocks in the 70 years
since they were quarried has weakened the external
material. This is reflected both in megascopic
observation once blocks are cut, and by
increase in test results on internal samples.
Sample test results from exterior material
are substandard or marginal for Absorption
(C97), Abrasion Resistance (C241), and Compressive
Strength (C170). Test results for these
parameters when run again on less weathered
sample all improve into the acceptable category
according to ASTM recommendations. CGS has
been advised by the Indiana Geological Survey
and is under the opinion that test results from
the interior, unweathered zone are more
representative of Conundrum Creek marble
physical properties. The marble tested meets or
exceeds required ASTM standards.
POTENTIAL CONUNDRUM
CREEK PRODUCTS
The products listed below are described from
the field mapping and sampling investigations
which were greatly hindered by lack of
outcrop, from extreme contortion of beds and
from gradation of one marble color into another.
The representative samples have been
described in Appendix A.
30
Black Marble (Pbbmc)
The marble identified as black marble in previous
reports and newspaper articles is in fact
a medium to coarse grained, medium gray. There
is also a fine grained, thin bedded, dark gray
marble occurrence interbedded with hornfels.
This darker marble was not observed to outcrop
in sufficient thicknesses nor in continuous
enough beds to mine. The medium gray marble
was previously mined from the northern most
exposure of marble outcrop from two benches
separated by 30 feet. Approximately 400 tons
were taken from this area, skidded down to a
loading bench and removed from the property.
Very little waste remains from this operation.
This area is proposed to be the phase one
mining area. The outcrop here is approximately
100 feet long, north to south, and the same in
an east to west direction. This bed of uniform
marble can be projected southward to the lower
waterfall giving it a strike length of 500 feet.
The true thickness of this bed is 80 feet but
chert beds in the lower portion reduce the
mining thickness to 65 feet. These beds change
from fairly flat lying (a slight westerly dip) to a
considerable northerly dip just north of the old
quarry. CGS projects these beds into the hillside
500 feet which would yield 16 million cubic
feet or 1.4 million tons at 175 pounds per cubic
foot (pel). Figure 17 is a photo of a polished slab
of gray marble cut from an old stockpile block
from the 1912 Colorado-Highland operation.
CGS recovered the block and had a polished
finish put on a face by Denver Marble Company.
Gray Marble (Pbgm)
Beds of gray marble have been observed on the
property in various stratigraphic intervals.
These gray beds range in color from light gray
to light blue. They also range from coarse to
fine grained. They are seen in outcrop at the
southern portion of the property and where
they are interbedded in thin beds with the
previously mined dark gray marble and with
beds of white marble throughout the property.
These beds appear to be too thin, discontinuous,
and jointed to be mined for quarry blocks
(Figure 18).