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POPULAR SCIENCE REVIEW. 
Silicic acid 
Lead oxide 
Manganese protoxide 
Lime 
Magnesia . 
Alkalies, &c. 
. 34*55 
. 34-89 
. 20-01 
. 4-89 
. 3-68 
. 1-86 
99-88 
On one specimen, which appeared to be ganomalite in the crystallized 
condition, the angle between two planes of cleavage was found to be 104° 33'. 
The last of the minerals mentioned in this interesting paper has been termed 
jacobsite. It has strongly developed magnetic characters, and contains, in 
addition to some constituents which are apparently accidentally present, the 
following oxides : 
Iron oxide . 
Manganese oxide . 
Manganese protoxide 
Magnesia 
8*39 per cent. 
6-96 
The formula of jacobsite appears therefore to be Mn0(Fe 2 0 3 , *Mn 2 0 3 ). 
Adamite. — This mineral, a zinc arsenate, hitherto met with at Chanarcillo, 
Chili, and the Mine de la Garonne, has been found by Laspeyres in the 
calamine deposits of Laurium. It forms small crystals of a greenish hue, and 
occurs in the cavities of the rose-red or reddish massive ore of the Greek 
mines, associated with arseniosiderite, crystallized smithsonite, and some- 
times with mimetesite. Its crystallographic characters were found not to 
differ materially from those of the specimens of adamite from Chanarcillo. 
Braun draws attention ( Jahrbuch fur Mineralogie, 1878, 188) to the inte- 
resting group of minerals, more than twenty in number, occurring in the 
Laurium beds, and points out the advantages which would accrue to science 
if they could be examined in situ by a good mineralogist. The ore which is 
now being raised is calcined before it is shipped and the minerals associated 
with the calamine are consequently destroyed. 
The Separation of Minerals of Different Specific Gravities. — Church has 
recently called attention to the applicability of Sonstadt’s solution to the 
separation of minerals of different specific gravity. The liquid consists of a 
solution of mercury iodide in potassium iodide, and is prepared by adding 
them alternately to the solution until no more of either is dissolved. A little 
free iodine occasionally colours the liquid, but this can be removed by the 
addition of some sodium hyposulphite. The light straw coloured liquid thus 
obtained may possess a specific gravity of 3*01 and can be employed for the 
separation of the mechanically loosened ingredients of any rock which it is 
desired to examine. Hardman describes the successful isolation by this means 
of a mineral occurring in a basalt of the North of Ireland. He used a 
solution having a specific gravity of 2*40, and was enabled to isolate two 
grammes of a mineral having a specific gravity of 1*70. This quantity the 
author questions his ability to have extracted after months of labour by any 
other method. He points out that it will now be possible to completely 
separate the three constituent minerals of granite — mica, felspar, and quartz, 
to weigh them and to determine almost absolutely their percentage, a 
problem which has as vet only been solved bv mathematical calculation, 
