256 DESCRIPTIONS OF MINERALS. 



disseminated in basaltic rocks, which never so occurs ; and 



in its cleavage. From obsidian or volcanic glass it differs 

 in its infusibility. 



Obs. Occurs as a rock formation : also disseminated 

 through basalt and other eruptive rocks, and is a charac- 

 teristic mineral of some varieties of them. Has been 

 found in New Hampshire, Canada, and elsewhere. As a 

 rock it occurs in North Carolina, and Pennsylvania. It 

 also occurs in many meteorites. Boltonite, from limestone 

 at Bolton, Mass., is a variety of chrysolite. 



Sometimes used as a gem, but it is too soft to be valued, 

 and is not delicate in its shade of color. 



For ste rite is a magnesian chrysolite Mgo 4 Si ; Fayalite, an iron 

 chrysolite, Fe 2 4 Si ; 3Tonticellite, a calcium-magnesium, CaMg 2 4 Si 

 Hortonolite, an iron-magnesium chrysolite from Orange County, N. T. 

 Rrepperite, an iron-manganese-zinc chrysolite from Stirling Hill, N.J. 

 Trphroite, a manganese chrysolite Mn 2 O, Si, from Stirling Hill, X. J. r 

 K/iehelite, a manganese- iron chrysolite, MnFe0 4 Si, from Dannemora, 

 Sweden. 



Leucophanite and mdiphantie are species containing the element 

 glucinum (beryllium), the former greenish yellow and G=2 97, the 

 latter yellow and G = 3*018. From Norway. 



Wohlerite contains zirconium, and also columbium ; color light yel- 

 low. G=3 41. 



Willemite is a zinc unisilicate, Zn 2 4 Si. See page 157. 



Dioptase is a copper silicate, which, making the water basic, is a 

 unisilicate, H 2 Cu0 4 Si. See page 141. 



Friedelite is a rose-red manganese silicate of the general formula 

 R 2 0^ Si . in which R consists of manganese and hydrogen in the atomic 

 ratio 2:1. 



Helvite (Helvinl Isometric ; in tetrahedral crystals. Color honey- 

 yellow, brownish, greenish. Lustre vitreo - resinous. H. =6-6'5. 

 G. =31 33. Contains manganese, iron, and glucinum, and some 

 sulphur. From Saxony, and Xorway. 



Danalite. Isometric ; in octahedral crystals. Color flesh-red to 

 gray. Lustre vitreo-resinous. H. =55. G.=3'427. Contains zinc, 

 glucinum, iron, manganese. Found disseminated through the granite 

 at Rockport, Cape Ann, Mass., and also near Gloucester, Mass. 



Eulytite is a bismuth silicate, and Bismutoferrite a bismuth-and- 

 iron silicate. 



Garnet. 



Isometric. Common in dodecahedrons (fig. 1), also in 

 trapezohedrons (fig. 2), and both forms are sometimes vari- 

 ously modified. Cleavage parallel to the faces of the dode- 

 cahedron ; sometimes rather distinct. Also found massive 

 granular, and coarse lamellar. 



