44 
IOWA ACADEMY OF SCIENCE Voi.. XXVIII, 1921 
Specimen from Tuchshoe, New York , — Traces of iron 
color the otherwise milk-white crystals. They are rhombohedral 
in form, hard, and possess a bright lustre. The specific gravity is 
2.84. 
PER CENT 
SiO^ 0.45 
1.10 
Alfi^ 0.16 
CaCOg 52.16 
MgCOg.... 46.80 
99.76 
24. Specimen from Guanajuato, Mexico .- — The specimen is 
white, with visible traces of iron oxide. The crystals are hard and 
hexagonal in form. We were not able to determine the specific 
■ PERCENT 
SiO^ 86.76 
Fe203 5.50 
AI 3 O 3 4.33 
CaC03 0.75 
MgC 03 2.11 
99.45 
2^. Specimen from Clayton, Iowa . — This takes a good polish 
and then it resembles brown marble. It belongs to the Platteville 
formation of the Ordovician system. The specific gravity is 2.69. 
PER CENT 
SiOg 0.87 
Al^Og and Fe 203 1.01 
CaC03 53.34 
MgC03 44.44 
99.66 
26. Specimen from Dubuque, Iowa . — It is of a gray color and 
quite compact in texture. It belongs to the same geological forma- 
tion as the preceding. percent 
SiOg 7.29 
A1 O and Fe O 3.00 
CaC03 46.94 
MgC03 42.89 
100.12 
2y. Specimen from White 'Fine, Nevada . — The rhombohedral 
crystals are on a brown and gray surface, and are rather soft. The 
crystals on analysis were found to contain a small amount of cop- 
per. We were not able to determine the specific gravity. 
