SPINEL. It I 



is attracted by the magnet. Zircon has a high specific 

 gravity and is not so hard. 



Obs. Occurs in granular limestone ; also in gneiss and 

 volcanic rocks. At numerous places in the adjoining coun- 

 ties of Sussex in New Jersey, and Orange county, of various 

 colors from red to brown and black ; especially at Franklin, 

 Newton and Sparta, in the former, and in Warwick, Amity 

 and Edenville, in the latter. The crystals are octahedrons, 

 and often grouped or disseminated singly in granular lime- 

 stone. One crystal found at Amity by Dr. Heron, weighs 

 49 pounds. The limestone quarries of Bolton, Boxborough, 

 Chelmsford and Littleton, Mass., afford a few crystals. 



Crystals of spinel are occasionally soft, having undergone 

 a change of composition, and approaching steatite in all 

 characters except form. They are true pseudomorphs. They 

 are met with in Sussex and Orange counties. 



Uses. The fine colored spinels are much used as gems. 

 The red is the common ruby of jewelry, the oriental rubies 

 being sapphire. Crystals weighing 4 carats have been 

 valued at half the price of a diamond of the same size. 



Automolite. A variety of spinel, containing 20 — 35 perct. of oxyd 

 of zinc. Color dark green or black. H=7*5 — 8. Gr=4 — 4'6. With 

 soda it forms at first a dark scoria, and when fused again with more 

 soda, a ring of oxyd of zinc is deposited on the charcoal. Infusible 

 alone, and nearly so with borax. 



Occurs in granite at Haddam with beryl, chrysoberyl, garnet, &c. In 

 Sweden, near Fahlun, in talcose slate. 



Dysluite. A variety of the species spinel, containing oxyd of 

 iron and zinc. Color yellowish or grayish-brown. H=75 — 8. G= 

 4*55. Composition, alumina 30'5, oxyd of zinc 16'8, peroxyd of iron 

 419, protoxyd of manganese 76, silica 3, moisture 0*4. Becomes red 

 before the blowpipe, but loses the color on cooling. Infusible alone 

 with borax affords a translucent bead of a deep garnet-red color. The 

 name dysluite is from the Greek dus, with difficulty, and luo, to dis- 

 solve. From Sterling, N. J., with Franklinite and Troostite. 



Hercinite. A spinel consisting of alumina and protoxyd of iron, with 

 only 29 per cent, of magnesia. 



3. Hydrous combinations with Silica, 



halloysite. — Hydrous Silicate of Alumina. 

 Massive and earthy, resembling a compact steatite. 

 Yields to the nail, and may be polished by it. 



How is spinel distinguished from magnetic iron 1 from garnet ? from 

 zircon? For what are spinels used? What is automolite? What ia 

 the appearance of halloylite ? 



14* 



