1895.] Mineralogy. 565 
Serpierite.—This mineral, which comes from the Laurium Mts. in 
Greece, was described by Bertrand and Des Cloiseaux’ and Damour in 
1881, but no analysis was made of it. Damour described it as an in- 
soluble hydrated basic sulphate of zinc and copper. Frenzel? has re- 
cently analyzed the mineral and found it to contain eight per cent of 
lime and very minute quantities of aluminium, chlorine, and sodium. 
The analysis is as follows: CuO 36.12, ZnO 13.95, CaO 8.00, SO, 24.29, 
H,O 16.75, Total 99.11. This corresponds to the empirical formula 
3 (CuO ZnO CaO) SO,+-3H,0. 
Lautite.—This mineral has been considered a mixture by Groth 
and Weisbach. A new find from the Rudolf Schachte at Lauta, near 
Marienberg, Sax., is according to Frenzel’ very pure, though it never 
occurs in crystals or even in large masses. The following analysis by 
him he considers sufficient evidence that lautite is an independent 
mineral ; 
Percentages. Molecular ratios. 
Cu 36.10 0.568 
As 45.66 0.608 
; 17.88 0.559 
99.64 
The content of silver in the mineral varies from 0-12 per cent, and 
perhaps more. 
Study of Optical Anomalies by Artificially Coloring.— 
Senarmont and later Otto Lehman showed that anisotropic crystals 
may be artificially colored by adding coloring matter to the solution 
in which they are forming. They thus become pleochroic. Gaubert”? 
utilizes this fact in examining some pseudo-isometric crystals—the an- 
hydrous nitrates of barium, lead, and strontium. The colored crystals 
obtained show six pleochroic sectors at the same instant, the opposite. 
sectors having the same tint. Ifa barium nitrate solution be divided 
into two parts and one of these be colored with methelene blue, the 
colored erystals obtained have intense pleochroism, although the un- 
colored crystals from the other part of the solution exhibit no double 
refraction. 
1 Bull. Soc. Minéral. de France, iv, p. 89, 1881. 
ë Min. u. petrog. Mitth., xiv, pp. 121-130, 1894. 
° Ibidem, . 
_ WBull. Soc. Franç. Minér., xvii, pp. 121-123, May, 1894. 
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