408 Minerals recently investigated by M. Hermann. 
Art. XLI.—On some Minerals recently investigated by 
M. Hermann ;* by James D. Dana. “ 
1. GrppsiTE. 
Tue analyses of Gibbsite by Hermann, according to which 
Gibbsite is a phosphate instead of a hydrate of alumina,* are al- 
luded to by Prof. Silliman, Jr., in his memoir, in volume vii, of 
this Journal, page 411, where this chemist, by several analyses, 
sustains the original view with regard to this species, his results 
giving much less than one per cent. of phosphoric acid. Her-_ 
mann in a late memoirt publishes the following as his recent 
conclusions upon the Richmond mineral. ; 
la, 16. 2. he, 
Phosphoric acid, . . 87-62 26°30 15°30 19 
Alomina;. >). +. 96-66 38:29 50-20 53-92 
gee ere ae 35:41 3450 34:18 
Nos. la and 14 were two specimens somewhat foliated on limo- 
nite; G.=2-21. No.2 was a stalactitic mass; G.=2-44. No.3 
was porous with an earthy fracture; G.=2-20. The phosphoric 
acid is here made a very varying constituent. 
This species, from Richmond, has recently been analyzed by 
Mr. Crossley in the Laboratory of Dr. C. 'T’. Jackson, with direct 
reference to the occurrence of phosphoric acid (as in Prof. Silli- 
man’s investigations), and he has found that his specimens con- 
tained no phosphoric acid, and were a true hydrate. ‘The mineral 
is therefore identical with Rose’s hydrargillite and includes that 
" species, as has been before suggested. 
2. Wittemitr, or Annyprous Suicate or ZINe. 
The anhydrous silicate of zinc was first recognized as a species 
by Vanuxem and Keating, who published a full and accurate de- 
scription both physical and chemical, in 1824, in the Journal of 
the Academy of Natural Sciences of Philadelphia, volume iv, 
Surling, New Jersey, and give the angle R: R, 118°, which was 
offered as only an approximation, the faces being irregular and 
rough. 
Subsequently, Dr. Thomson of Glasgow received specimens. 
He described the mineral physically nearly as done by Vanuxem 
and Keating,t mentioning the hexagonally prismatic form with 
trihedral summits, though giving the angle 124° instead of 118°, 
observing however that it was “impossible to measure the an- 
gles,” as the planes were so very uneven. He states that the 
Leer 
* Jour. fir Prakt. Chem, xl, 32. + Ibid, xlvii, 1. 
- $ Ann. Lyceum Nat. Hist, N.Y, iii, 1828, and Mineralogy, 1836, i, 519. 
