LEUCITE. 175 



Color dark brown or black. Luster vitreous, inclining to 

 resinous; sometimes bright, but often dull. Translucent to 

 opaque. H=7— 7-5. Gr=3-65— 373. 



Composition: silica 29*3, alumina 53*5, peroxyd of iron 

 17*2. Before the blowpipe it darken?, but does not fuse. . 



Dif. Distinguished from tourmaline and garnet by its 

 infusibility and form. 



Obs. Found in mica slate and gneiss, in imbedded 

 crystals. 



Very abundant through the mica slate of New England. 

 Franconia, Vt. ; Windham, Me. ; Lisbon, N. H. ; Chester- 

 field, Mass. ; Bolton and Tolland, Ct. ; on the Wichichon, 

 eight miles from Philadelphia, and near New York city, are 

 some of the localities. St. Gothard in Switzerland, and the 

 Greiner mountain, Tyrol, are noted foreign localities. 



The name staurotide is from the Greek stauros, a cross. 



LEUCITE. 



Occurs only under the form of the trapezohedron, as in the 

 annexed figure. Cleavage imperfect. Usually 

 in dull glassy crystals, of a grayish color ; some- 

 times opaque-white, disseminated through lava. 

 Translucent to opaque. H=5*5 — 6. Brittle. 

 Gi— 2*48— 2/49. 



Composition : silica 55*1, alumina 23*4, potash 21*5=100, 

 Infusible except with borax or carbonate of lime, and ther 

 with difficulty to a clear globule. A fine blue color, with 

 cobalt solution. 



Dif. Distinguished from analcime by its hardness and 

 infusibility. 



Obs. In lavas, especially those of Italy. Abundant at 

 Vesuvius. Crystals from a pin's head to an inch in di- 

 ameter. 



The name leucite is from the Greek leukos, white. 



Saccharite resembles a granular feldspar, of a white or greenish- white 

 color, but has the constitution of leucite. Infusible alone, and with 

 great difficulty with soda. From Silesia. Perhaps Andesine. 



What are the colors and hardness of staurotide ? What is its con- 

 stitution? What is its mode of occurrence? How is it distinguished 

 from tourmaline ? Describe the forms and appearance of leucite. How 

 does it differ from analcime ? 



