MINEKALOGV. f)9f) 



jj[reeu j tiaiisparciit. The optic axes lie in a plauc parallel to the brachy- 

 I)inacoid, and the bisectrix is negative and normal to the basal plane; 

 the axial angle is large, 80° for green rays, measured in a solution of 

 mercuric iodide in potassium iodide (w= 1-722). The pleochroism is 

 distinct. An analysis yielded the following results: 



N2OS CnO H2O 



22-76 66-38 11-26 = 100-40 



The formula calculated, viz, 4CuO, ^"205, 3H2O, requires ISTjOr, 22-52, 

 CuO 60-22, H2O 11-56 = 100, agreeing closely with the results of analy- 

 sis. The mineral is named after the chemist who first determined the 

 true composition of the corresponding artificial compound. This arti- 

 ficial salt, as noted on a previous page, has also been made by Wells 

 and Peufield and shown to crystallize in themonocliuic system ; the form, 

 however, is rather closely related to that of the orthorhombic gerhard- 

 tite. 



Graphitoid. — This name has been given by Sauer to a substance which 

 he regards as amorphous carbon. It occurs extensively in the mica 

 schists and phyllites of the Saxon Erzgebirge. It forms loose incrusta- 

 tions on the surfaces of the schist, shows no crystalline structure, and 

 burns with comparative rapidity in a Bunsen burner. An analysis of 

 the combustible substance gave — carbon, 99-76; hydrogen, 0-24 = l()(>; 

 showing that it is essentially pure carbon. Besides occurring as an in- 

 crustation it also impregnates the rock mass, forming fine bands of mi- 

 nute particles passing in parallel directions through the irregular quartz 

 grains. The author recognizes the fact that true graphite is also a 

 common constituent of many archaeau rocks, but suggests that with it 

 the graphitoid may also be present. A related form of amorphous car- 

 bon was described a few years ago by von Inostranzeff, also from phyl- 

 lite. 



HanJcsite. — A new anhydrous sulphato-carbonate of sodium, described 

 by W. E. Hidden, obtained from San Bernardino County, California, 

 where it occurs with thenardite, borax, &c. It is named after Mr. 

 Henry G. Hanks, State mineralogist of California. Hanksite crystallizes 

 in the hexagonal system, the crystals being short hexagonal jirisms 

 with one or two pyramids and the basal plane; they sometimes form 

 confused groups of tabular six-sided crystals. Optically it is uniaxial, 

 negative. The hardness is 3 — 3-5, and the specific gravity 2-562. The 

 color is white, inclining to yellow; the crystals nearly transparent, 

 though sometimes inclosing impurities. An analysis by J. B. Mackin- 

 tosh gave the results unaer I, below ; another analysis by S. L. Penfield, 

 made two years since upon a large crystal from California (exact locality 

 unknown), is given under II . 



SO3 



1 45-89 



II 43-59 



