262 DESCRIPTIONS OF MINERALS. 



boldtilite) is a related dimetric species, from Capo di Bove, 

 near Koine, and Mount Somma, Vesuvius. 



Epidote. 



Monoclinic. mAI i=115° 24'. t-t A —1-4=116° 18'. — 1a 

 -1 = 109° 35'. Cleavage parallel to 

 i-i ; less distinct parallel to 1-i. 

 Also massive granular and forming 

 rock masses ; sometimes columnar 

 or fibrous. 



Color yellowish green (pistachio- 

 green) and ash-gray or hair-brown. Streak uncolored. 

 Translucent to opaque. Lustre vitreous, a little pearly 

 on i-i ; often brilliant on the faces of crystals. Brittle. H. 

 = 6-7. G. = 3-25-3'5. 



Composition. A lime iron-alumina silicate, the iron being 

 mostly in the sesquioxide state and replacing aluminum. 

 Percentage of common variety, Silica 37*83, alumina 22*63, 

 iron sesquioxide 1502, iron protoxide 0'93, lime 23*27, 

 water 2-05=100-73. 



B.B. epidote fuses with effervescence to a black glass 

 which usually is magnetic. Partially decomposed by hy- 

 drochloric acid, but if first ignited, is then decomposed, 

 and the solution gelatinizes on evaporation. 



Green epidote is often called Pistacite. Piedmontite is 

 a variety containing much manganese, of reddish -brown or 

 reddish-black color. 



Bucklandite is an iron-epidote. 



Diff. The peculiar yellowish-green color of ordinary epi- 

 dote distinguishes it at once. From zoisite and vesuvian- 

 ite it differs in fusing to a black magnetic globule. 



Obs. Occurs in crystalline rocks, especially in hornblen- 

 dic rocks. It often occurs in the cavities of amygdaloidal 

 rocks. Splendid crystals, six inches long, and with bril- 

 liant faces and rich color, have been obtained at Haddam, 

 Ct. Crystallized specimens are also found at Franconia, 

 N. H. , * Hadlyme, Chester, Newbury and Athol, Mass. ; 

 near Unity, Amity, and Monroe, N. Y. ; Franklin and 

 Warwick, N. J. ; Pennsylvania, at E. Bradford ; Michigan, 

 in the Lake Superior region ; Canada, at St. Joseph. 



The name epidote was derived by Hauy from the Greek 

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

 of the primary is frequently much enlarged in the crystals. 



