144 



MAGNESIA. 



Indurated talc. A slaty talc, of compact texture, and 

 above the usual hardness, owing to impurities. Feel some 

 what unctuous. • This passes into taJcose slate, still less 

 pure and less unctuous in its feel, and coarser in its slaty 

 structure. 



Rensselaerite. This name has been given by Professor 

 Emmons to a kind of soapstone from St. Lawrence, Jeffer- 

 son county, N. Y., which has a very compact structure, a 

 soapy feel, slight transl acency, and hardness 3 to 4. It oc- 

 curs of white, yellow, or grayish white colors, and even 

 black. It works up with a very smooth and handsome sur- 

 face, and is made into inkstands. 



Composition of foliated talc, silica 62-8, magnesia 32*4, 

 with pyotoxyd of iron 1*6, alumina 1*0, water 2*3. Water 

 is considered by some chemists an essential ingredient, and 

 4 per cent, have been detected in some talcs. 



Composition of steatite, silica 62*2, magnesia, 30*5, pro- 

 toxyd of iron 2*5, water 5*0. Before the blow-pipe talc loses 

 its color and fuses with great difficulty. 



Dif. The unctuous feel, foliated structure, and pearly 

 uster of talc are good characteristics. It differs from mica 

 also in being inelastic, although flexible ; from chlorite, 

 saponite and serpentine in yielding no water when heated 

 in a glass tube. Only the massive varieties resemble the last 

 mentioned species, and chlorite has a dark olive-green color. 



Obs. Handsome foliated talc occurs at Bridgewater, Vt. ; 

 Smithfield, R. I. ; Dexter, Me. ; Lockwood, Newton and 

 Sparta, N. J., and Amity, N. Y. On Staten Island, near 

 the quarantine, both the common and indurated are obtained ; 

 at Cooptown, Md., green, blue and rose colored talc occur. 

 Steatite or soapstone is abundant, and is quarried at Graf 

 ton, Vt., and an adjacent town ; at Francestown and Orford, 

 N. H. It also occurs at Keene and Richmond, N. H. ; at 

 Marlboro and New Fane, Vt. : at Middlefield, Mass. ; in 

 Loudon county, Va., and at many other places. 



Uses. Steatite may be sawn into slabs and turned in a 

 lathe. It is used for lire stones in furnaces and stoves, and 

 for jambs for fire-places. It receives a polish after being 

 heated, and has then a deep olive-green color. It is bored 

 (;ut for conveying water, in place of lead tubes. Steatite is 



How does talc differ from mica 1 Of what does talc consist ? Why 

 i? it useful for fire stones? What other uses has it ? 



