26 
AN INVESTIGATION INTO 
WHITE MARBLE, CARRARA, ITALY. 
A white, very fine grained saccharoidal marble. Under the microscope it 
is seen to consist of a mosaic of calcite grains. In this mosaic some grains are 
larger than others, but there is no great difference in their relative sizes and 
the average grain of the rock is uniform throughout. The average diameter 
of calcite crystals closely approximates 0-2 mm. The grains come against one 
another along sharp and usually straight lines. There is no trace of foliation 
in the rock, nor is there any trace of flattening or elongation of the grains 
in any one direction. The rock is perfectly massive. Between, crossed 
nicols the calcite individuals extinguish uniformly and show no signs of 
pressure. Some of them show a few twin lamellae. 
A color-process photograph of a polished surface of the rock employed 
is shown in Plate II A and a photomicrograph of a thin section of the rock, 
taken in ordinary light and magnified 27 diameters, is shown in Plate II B. 
Three specimens of the rock were used in measuring the elastic constants, 
two square prisms (a and b) and a round column (c). Two sets of measure- 
ments were made on both b and c, the instrument being as usual affixed to 
the specimen in two positions at right angles to one another in each specimen. 
In this way five complete sets of measurements were made. The results are 
set forth in the table on page 27. 
The means of the results obtained for the respective elastic constants are 
as follows: 
E= 8,046.000; <r=o.2744; #=5,946,000; C= 3, 154,000. 
The difference between the highest and lowest determinations of D is 420,000 
pounds. 
9000 
1000 
240 
FIG. 7. Carrara marble, specimen a. Stress-strain curves- 
Figure 7 shows the results obtained from specimen a in graphic form. 
I represents longitudinal compression and II lateral extension. The hys- 
teresis is greater than in the case of Belgian black or Tennessee marble, but 
is about the same in amount' as that shown by the Vermont marble and 
the Trenton limestone from Montreal. 
