40 PROCEEDIlirGS OP THE NATIONAL MUSEUM vol. 71 



CALCITE 



Calcite occurs as colorless " dogtooth " crystals averaging 5 nun, 

 or more in length lining open cavities in seams in a dark gray 

 limestone containing abundant finely disseminated pyrite. The 

 calcite overlies a first lining of the open spaces which consists of a 

 ferriferous dolomite or ankerite which weathers brown and, where 

 it forms free surfaces, develops saddle-shaped aggregates of curved 

 rhombohedral crystals. The calcite is all of similar habit and, is 

 rather simple, the forms present beiner (1122), (2241), (4481), 

 and (4151). The habit is essentially as shown in the drawing. 

 Figure 16. The faces of /(1122) are striated vertically as shown 

 and give poor reflections. -^(2241) is rounded and gives no signals 

 but was identified by its zonal position. The other faces are bright. 



PTRITE 



Pyrite is generally distributed in the specimens associated with 

 nearly all of the other minerals. It forms scattered crystals up to 

 nearly 1 cm. in diameter, practically all of which have been com- 

 pletely altered and are now glossy pseudomorphs of hard vitreous 

 limonite. While the crystal form is in a few places dominated by 

 the pyritohedron or octahedron, the majority of the crystals are of 

 complex appearance, and their development is probably controlled by 

 diploids. The crystallography was not completely worked out. 



Indistinct small crystals of pyrite altered to limonite occur in 

 small vugs in massive garnet rock, overlying small crystals of grossu- 

 larite. Scolecite and a little chabazite are associated with ihe pyrite 

 and appear to be later than it (No. 84553) . Scattered crystals of pyrite 

 occur in cavities in specimens containing anorthite, adularia, titanite, 

 epidote, and chlorite. The pyrite crystals, which reach 8 mm. m 

 diameter and are of complex form, are probably the last mineral 

 deposited in this assemblage. They are altered to limonite pseudo- 

 morphs (No. 84560). Similarl}^ pyrite crystals up to 1 cm. in diam- 

 eter occur in coarse brown grossularite garnet (No. 84559). Pyrite 

 crystals ranging from minute to a diameter of 2 mm., the form of 

 which is dominated by the pyritohedron, rest upon a crust of small 

 green garnets. These are younger than the adularia crystals of the 

 same specimen (No. 84576). Complex pyrite pseudomorphs, 3 mm. 

 in diameter, which rest on vesuvianite, are apparently older than 

 the prismatic quartz crystals which line the same cavity (No. 84559). 

 Crystals up to 5 mm. in diameter rest upon mizzonite in a specimen 

 composed of radiating mizzonite prisms (No. 84567). 



