KPIDOTE. 183 



Color yellowish-green (pistachio-green) and ash or haii 

 brown. Streak nncolored. Translucent to opaque. Lus. 

 ter vitreous, a little pearly on M ; often brilliant on the faces 

 of crystals. Brittle. H=6—7. Gr=3'25— 3-46. 



Varieties and Composition, There are three prominent 

 varieties of this species ; one of a yellowish-green color, 

 another called zoisite, of a grayish-brown or hair-brown ; a 

 third of dark reddish shades, which contains 14 per cent, of 

 oxyd of manganese, and is called Manganesian epidote. 

 Thulite is another red variety, of paler color. 



The yellowish-green epidote is sometimes called Pistacite. 

 The mineral Bucklandite is an iron-epidote. 



The green epidote consists of silica 37*0, alumina 26*6, 

 lime 20'0, protoxyd of iron 13*0, protoxyd of manganese 0.6, 

 water 1*8. 



Zoisite consists of silica 40*2, alumina 30*3, lime 22*5, 

 peroxyd of iron 4*5, water 2.0. Before the blowpipe, epidote 

 and zoisite fuse on the edges and swell up, but do not liquefy. 

 The manganesian epidote and thulite fuse readily to a black 

 glass. 



Dif. The peculiar yellowish-green color of ordinary ep- 

 idoie distinguishes it at once. The prisms of zoisite are 

 often longitudinally striated or fluted, and they have not the 

 form or brittleness of tremolite. 



Obs. Occurs in crystalline rocks, and also in some sedi- 

 mentary rocks that have been heated by the passage of dykes 

 of trap or basalt. Splendid crystals, six inches long, and 

 with brilliant faces and rich color, have been obtained at 

 Haddam, Ct. Crystallized specimens are also found at Fran- 

 conia, N. H., Hadlyme, Chester,[ Newbury and Athol, Mass., 

 near Unity and Monroe, N. Y., Franklin and Warwick, N. 

 J. Zoisite in columnar masses is found at Willsboro and 

 Montpelier, Vt., at Chester, Goshen, Chesterfield, and else- 

 where in Massachusetts ; at Milford, Ct. 



The name epiUote was derived by Hatty from the Greek 

 epididomi, to increase, in allusion to the fact that the base of 

 the primary is frequently much enlarged in the crystals. 



The mineral Allanite, p. 207, is near epidote in form and 

 composition, although containing cerium. 



What are the colors and other characters of epidote ? What is the col- 

 or of the variety zoisite? What is the composition of epidote? what 

 ire its distinguishing characters? 



