CLAYS OF NEW YORK 505 



Halloysite. A massive, clay-like or earthy mineral, with a 

 conchoidal fracture. It shows little or no- plasticity. It has a 

 hardness of 1-2. The specific gravity is 2.0-2.20. The luster is 

 somewhat pearly tO' waxy or dull. The color is white, grayish, 

 greenish, yellowish and reddish. It is translucent to opaque, some- 

 times becoming translucent or even transparent in water, with an 

 increase of one fifth in weight. It is a silicate of alumina like 

 kaolinite, but amorphous and containing more water; the amount 

 is somewhat uncertain, but according to Le Chatelier the composi- 

 tion is probably 2II2O, AloOg 28102+ aq, or silica 43.5^, alumina 

 36.9^, water 19.6^= 100. It is not uncommon in the kaolin de- 

 posits around Valleyhead, Dekalb co. Ala., where it occurs as 

 veins in the kaolin. 



Kectorite. Monoclinic. In leaves or plates resembling moun- 

 tain leather. Very soft, hardness less than that of talc. Feell 

 soapy. Luster pearly. Color pure white, sometimes stained red 

 with iron oxid. Composition: H Al SiOiOr AlaOg, 2 SiOj, Il20= 

 silica 50.0; alumina 42.5; water Y.5. 



Newtonite. Rhombohedral. In soft, compact masses, resem- 

 bling kaolinite. Color white. Composition: H8A]2Si20ii+ water 

 or AlgOg, 2 SiOo, 5 Il20=silica 3S.5, alumina 32.7, water 28.8, 

 Sp. gr.==2 37. 



AUophane. Amorphous. As incrustations which are usually 



thin, with mammillaxy surface. Occasionally almost pulverulent. 

 Fracture imperfectly conchoidal and shining, to earthy. Very 

 brittle. Color variable. Translucent. A hydrous aluminum sili- 

 cate, Al2Si05-l-5H20=silica '^3.8, alumina 40.5, water 85.7. 

 Hardness ?.. Sp. gr. 1.85— 1 8'.\ 



Other species listed by Dana in the kaolinite group are cimohte, 

 montmorillonite, pyrophyllite, collyrite and Schrotterite. Indian- 

 aite, a white residual clay found in Lawrence co. Ind., is placed 

 under halloysite by Dana. 



Clays may vary mineralogically within very wide limits. Pure 

 clay, as before stated, would consist entirely of the mineral kaolin- 

 ite, but in addition to this quartz, feldspar and mica are minerals 



