Mineralogical Contributions — Hobbs. 183 
of the Grand river, coffer dams having been built and the 
rock quarried both for lime and for road metal. The lime- 
stone is traversed by a vertical vein of barite, containing 
well developed crystals. Two miles down the river the 
limestone dips under the well known gypsum beds of the 
vicinity. The rock in which the crystals here described 
were found, is a dark gray to white compact limestone with 
cavities which in many of the specimens were lined with a 
film of pyrite, to which the calcite crystals are attached. 
These crystals have been studied at the university by Mr. 
W. M. Kennedy. The habit of the calcite is either scalen- 
ohedral or rhombohedral, the latter variety being white 
and the former when found alone of a brownish-yellow 
color. Twins are common, the twinning plane being a face 
of the fundamental rhombohedron. Superimposed upon 
some of the larger crystals are numerous smaller and much 
distorted individuals so flattened as to resemble* in form the 
tooth of a shark, the orientation being, however, the same 
for both larger and smaller crystals. The following forms 
were observed : 
r, R (lOU) M, R V (7. 4. lT. 3) 
0, — £ H (0554) 1b, R I (11. 1G. 5 6) 
X,-|R (0994) and 
p, —3 R (0331) 1, — y R (11. 0. n. 3) doubtful. 
m, — v R (0. 11. 11. 3) 
v, R 3 (2131) 
