324 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



Per cent 



Magnesia (MgO) 0. 16 



Water (H 2 0— ignition) 2. 04 



Total . 100. 66 



The composition is thus that of a nearly iron-free zoisite. 



CLINOZOISITE (406a) 



Calcium aluminium silicate, Monoclinic. 



4Ca0.3Al 2 3 .6Si0 2 .H 2 0. 



ADAMS COUNTY 



Clinozoisite is listed, without further description, by Livingston 

 and Laney 52 ° as occurring in the eontact-metamorphic copper deposits 

 of the Seven Devils district. 



EPIDOTE (407) 



Silicate of lime, ferric iron and alumina, 



H 2 0.4Ca0.3(Al,Fe) 2 3 .6Si0 2 . Monoclinic. 



Epidote is a silicate which frequently occurs with other minerals 

 of similar origin at the contact of intrusive igneous rocks with lime- 

 stone, and also is found in a variety of other situations. The most 

 important locality thus far known in Idaho is in the Seven Devils 

 district in Adams County which, if carefully exploited, is probably 

 capable of furnishing fine cabinet specimens of this mineral. 



ADAMS COUNTY 



In Adams County epidote is abundant in the copper deposits of 

 the Seven Devils district, which are typical eontact-metamorphic 

 deposits in limestone. The mineral has been described by Palache, 53 

 whose description is largely reprinted in the following. The epidote 

 occurs in the Peacock and other mines in deep-green crystals in 

 cavities in the massive epidote. These crystals are sometimes 

 unusually large and fine, some of them reaching a length of 30 cm. 

 or more. Many of them are flattened parallel to the base c(001) 

 giving them a lozenge shape in cross section. They have the normal 

 epidote habit being elongated parallel to the b axis and are almost 

 invariably attached by an end of this axis. The majority of these 

 elongated crystals are terminated simply by n(Tll); others also 

 have 6(010) and in the orthodome zone they show c(001), ^(T02), 

 r(T01) , and a (100) . Some crystals are much richer in forms as shown 

 in Figures 92 and 93, which are orthographic projections on the 

 clinopinacoid showing distortion. Twinning is common according 



»2° Idaho Bur. Mines and Qeol., Bull. 1, p. 62, 1920. 



m Charles Palache. Amer. Journ. Sci., vol. 8, p. 299, 1899. 



