270 Mineral Resembling Meerschaum 



1. Hampdenite, analyzed by E. E. Nicholson, the University Of Minne- 

 sota. 



C. Hampshirite, fibrous coating, E. E. Nicholson, the University of 

 Minnesota. 



3. Hampshirite, inside of crystal, E. E. Nicholson, the University of 



Minnesota. 



4. Gray Serpentine, Brewsters, N. Y. Burt, Am. Jour. Sci., 1873, Vol. 



6, p. 210. 



5. Serpentine, chrysotile, Amelose, R. Brauns, Jahrbuch fiir Miner^l- 



ogie, 1887; Beil., Bd. v, 299. 



6. Serpentine, grass green, Porthalla, Collins, Quart. Jour. Geol. Soc. 



London, 1884, vol. 40, p. 467. 



7. Serpentine, calculated, Dana, System of Mineralogy, 6th ed. p. 691, 



1892. 

 Analyses 4 and 6 are quoted from Dana's System of Mineralogy, 

 6th edition, p. 672, and have not been further verified. 



Noting the variation in silica and iron in the first three analyses 

 Prof. Nicholson made a second and third determination of the iron with 

 the result that the inside of the hampdenite which was less exposed 

 to alteration yielded 10.24 percent of FeO which closely approaches 

 No. 2, and the outer portion which was somewhat stained and leached 

 yielded 8.07 percent of FeO. A second determination of the silica 

 using the white material from the inside of the mass gave 42.78 per cent 

 Si O,. showing that the larger percentage of silica in No. 1 is probably 

 due to alteration and loss of iron and magnesia. From these results 

 it is evident that from the chemical analyses there would be no rear 

 sen to make two separate varieties of these two substances, but the 

 texture is so different that the author feels warranted in giving the 

 name hampdenite to the massive splintery material as a distinct variety 

 cf serpentine while retaining the name hampshirite to indicate the 

 serpentine pseudomorphs after humite. 



The interior of the pseudomorphs is distinct from any serpentine 

 that has come to the author's notice, being compact and massive, with 

 an earthy feel and luster. The composition as determined by Prof. 

 Nicholson is decidedly different from that obtained by Dewey* who 

 obtained Si O, 50.60, Mg O 28,83, Al^ O3 0.15, FeO 2.59, MnO 1.10, H,0 

 15.00 — 98.27, which would approximate mere nearly the composition of 

 sepiolite than of serpentine. 



If the alumina and manganese be considered isomorphous with 

 the iron and the potash and soda isomorphous with magnesia the com- 

 position for both hampdenite and hampshirite may be considered as 

 H3 Fe^ Mgoi Slis 0;„ or 4 FeO, 21 MgO, 18 Si O,, 15 H^ O, which 

 would give a theoretic composition of approximately Fe O, 12; Mg O, 

 34; Si 0., 43; H,0, 11, which if we consider iron and magnesia to be 

 isomorphous is not far from the theoretic composition of serpentine. 



= Am. Jour. Sci., 1822-1823, vol. 4, 275; vol. 5, 249, vol. 6, 334. 



