42 IOWA ACADEMY OF SCIENCE Voi.. XXVIII, 1921 
from a mixture of the entire specimen. The specific gravity is 
SA 
PER CENT 
6.05 
FeA 
8.04 
AiA 
3.40 
CaC03 
59.43 
MgCOg 
22.85 
99.77 
15 . Specimen from Freiberg, Saxony. — The interior is finely 
granular and marble-like. The rhombohedral crystals on the ex- 
terior are brownish in color. The specific gravity is 2.87. 
SA 
PER CENT 
0.55 
FeA 
11.53 
AIA 
2.55 
CaCOg 
54.37 
MgCOg 
31.45 
100.45 
16 . Specimen from Lee, Massachusetts. — This rock is hard 
and white, resembling marble, with small shining rhombohedral 
crystals. The specific gravity is 2.87. 
SiO^ 0.64 
AI2O3 and 0.20 
CaCOg 65.30 
MgCOg 33.04 
99.98 
I/. Specimen from Biserf eld, Westphalia, Germany. — It is 
composed of large white crystals, irregularly set together,' and is 
accompanied by calcite and chalcopyrite. 
A few of the crystals 
are slate gray. The specific gravity is 2.80. 
PER CENT 
SA 
0.64 
FeA 
..... 11.49 
AIA 
2.28 
CaCOg 
..... 61.89 
MgCOg 
23.24 
100.41 
18 . Specimen from Niagara Falls, New York. — Irregular 
shaped crystals, which are pink, yellow, slate and black and are 
accompanied by calcite and selenite. The specific gravity is 2.8. 
PER CENT 
SiO^ 1.01 
FeA 1.26 
