SII.K Ml S, TITAN ATI.S. KTC. 501 



Like >erpentine, owing to the many sources from which it may 

 originate, it forms peeudomoipbfl after :i large number of minerals, 

 and even after species which contain no magnesi.um, as quart/, 

 top.i/., and cyanite, where the magnesium is furnished by perco- 

 lating waters. 



Talc is an abundant mineral, occurring under the same conditions 

 as the chlorites or serpentine ; it forms a large proportion of some 

 schists, which are termed talcose schists. It is also. found as len- 

 ticular masses in mctamorphic rocks, and magnetite, chromite, 

 hornblende, serpentine, and chlorites are associated minerals. 



Sepiolite (meerschaum), I^Mg&SiaOio, is a magnesium silicate 

 closely related to talc. Commercially talc finds many and varied 

 uses ; in the powdered form it is used as a paper filler ; in toilet 

 powders, paints, lubricants, and soaps. In slabs it is used in the 

 manufacture of hearthstones, table tops, vats, ovens, furnace 

 linings, stair treads, etc. 



All the Atlantic coast states are commercial producers of talc. 

 The fibrous variety is only found at Gouverneur, New York. 



KAOLINITE 



Kaolinite. Clay ; A basic orthosilicate of aluminium, H 4 Al2- 

 Si 2 9 ; A1 2 O 3 = 39.5, SiO 2 = 46.5, H 2 O = 14.0; Monoclinic; Type, 

 Digonal Equatorial ; a : b : c = .5748 : 1 : 1.5997 ; (3 = 83 11' = 

 100 A 001; 100 ,110 = 29 43'; 001 A 101 = 76 22' ; 001,011=57 

 48'; Common forms, b(010), c(001), m(110), n(lll); Twins 

 as in mica; Cleavage, basal perfect, flexible, inelastic, plastic, and 

 unctuous ; H. = 1-2.5 ; G. = 2.6-2.65 ; Color, when pure, white, 

 otherwise yellow, brown, red, or bluish ; Streak, white or pale ; 

 Luster, pearly to dull ; Transparent scales to translucent ; n = 

 1.54; v-a = .008; Axial plane J.010; Bx a A-L001 = 20 

 behind; 2E = 0-90. 



B.B. Infusible, becomes blue with cobalt solution. Yields 

 water in the closed tube and a silica residue in the S. Ph. bead. 

 Insoluble in acids. 



General description. In microscopic six-sided scales with 

 aniiles of nearly 120; also friable, mealy, or massive. When wet 

 it is plastic and has a peculiar greasy feel. When dry it absorbs 

 moisture from and sticks to the tongue and emits a peculiar argilla- 

 ceous odor just after being moistened. 



