508 REPORT OF NATIONAL MUSEUM, 1900. 



EPIDOTE. 



Epidote occurs in nionoclinic crystals, commonly prismatic and in 

 fibrous to granular masses having a hardness of 6 to T. a specific 

 gravity of 3.2 to 5, and a vitreous luster, inclining to pearly or 

 resinous on certain faces. Ordinarily the color is a peculiar yellow- 

 ish green, seldom seen in other minerals; from this it may pass into 

 light and dark shades, black on one side and brown on the other; red, 

 yellow, gray, and colorless varieties also occur. Epidote is doubly 

 refracting and strongly pleochroic, showing a green, a brown, and a 

 yellow as viewed in the several directions. 



Thulite is a closely related mineral occurring in orthorhombic forms 

 and in columnar to compact masses, having a specific gravity of 3.124 

 and a hardness of about 6.5. Its color varies from a peach-blossom 

 red to rose red; strongly pleochroic, showing a light rose, a deep rose, 

 and a yellow color in the different directions. 



Epidote is common in many crystalline rocks, as syenite, gneiss, 

 schist, and serpentine. It is sometimes found in geodes in trap, and 

 also in sandstone adjoining trap dikes, as a result of contact metamor- 

 phism. It occasionally forms with quartz an epidote rock, and is 

 sometimes found in nodules in the different quartz rocks or altered 

 sandstones. 



One hundred parts contain, approximately: Silica, 38; alumina, 22; 

 ferric oxide, 15; lime, 23; water, 2. 



EUCLASE. 



Euclase, named bj^ Hauy from €v^ easily, and kXcxco, to break, 

 though susceptible of a high polish, is rareh' used as a gem stone 

 because of its brittleness. It varies in color from pale mountain green 

 to indigo blue and white. Its hardness is 7.5, and its specific gravity 

 about 3.1. The mineral crj^stallizes in the nionoclinic system and 

 exhibits tj'ichroism. 



One hundred parts contain, approximately: Silica, 41.2: alumina, 

 35.2; glucina, 17.4; water, 6.2. 



Euclase occurs in the mining district of Villa Rica, Minas Geraes, 

 Brazil, associated with topaz in a chloritic schist. It is found also in 

 the auriferous sands of the Orenburg district of the southern Urals, 

 associated with topaz, corundum, kyanite, rutile, etc. 



FLUORITE. 



CHLOROPHANE. 



Fluorite crystallizes in the isometric system, commonly in cubes; 

 occurring also massive and graiuilar, coarse or fine. The mineral has 

 a perfect octahedral cleavage; a conchoidal to splintery fracture; is 



