246 
DESCRIPTIVE MINERALOGY. 
Uses. This salt, which is abundantly procured as a residue of the preparation of carbonic 
acid, etc., is employed, in consequence of its great attraction for water, to dry gases for ex¬ 
perimental purposes, and to separate water from various liquids. When heated so as to 
undergo watery fusion, there is obtained a powder which is used in the preparation of freezing 
mixtures. 
DATHOLITE. 
[From the Greek, signifying turbid .] 
Chaux Boratfc Siliceuse. Hauy. — Siliceous Borate of Lime. Clcavcland. — Prismatic Datolite. Jameson. — 
Prismatischer Distom Spatli. Mohs. — Borosilicate of Lime. Thomson. — Datholite. Beudant, Shepard and 
Dana. — (It includes Esmarkite, Humboltite and Botryolite. Thomson, however, describes the latter as a 
Description. Colour greyish or greenish 
white, rarely red and yellow. It occurs 
regularly crystallized and massive. The 
primary form is a right rhombic prism, Fig. 
119. M on M/ 103° 4CT (Phillips). Fig. 
120 is one of the secondary forms. Cleavage 
obtained with difficulty. Fracture uneven, 
conchoidal. Lustre resinous or pearly. From 
transparent to opaque. Hardness from 5.0 
When exposed to the flame of a candle, it 
becomes opaque, and crumbles down between the fingers. Before the blowpipe, it intumesces 
into a white mass, and then melts into a transparent or pale rose-coloured globule. It readily 
dissolves in, and gelatinizes with, nitric acid. If spirit of wine is burned upon the jelly, the 
flame is coloured green. 
Composition. According to Klaproth, it is composed of silica 36.50, lime 35.60, boracic 
acid 24.00, water 4.00. The Botryolite contains, according to the same chemist, silica 
36.00, lime 39.50, boracic acid 13.50, oxide of iron 1.00, water 6.50. 
Geological Situation. This mineral occurs in fissures and cavities in the greenstone and 
amygdaloid in New-York, and the contiguous parts of New-Jersey. 
localities. 
New-York County. This mineral is found in small quantities in cavities and veins in the 
greenstone boulders which are strewed over various parts of the island. 
Rockland County. At Piermont, where the New-York and Erie railroad passes through 
the greenstone, specimens of datholite have occasionally been found. They are highly modi¬ 
fied crystals. The finest specimens have, however, been obtained from fissures in this range 
distinct species.) 
Fig. 119. 
to 5.5. Specific gravity from 2.90 to 3.00. 
