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DESCRIPTIVE MINERALOGY. 
CLASS V. 
ALKALINE-EARTHY MINERALS. 
Composed of one or more alkaline earths, Baryta, Strontia, Lime or Magnesia, combined 
with water or an acid, and frequently containing some metallic oxide. 
ORDER I. BARYTA. 
1. Heavy Spar. 
f 
HEAVY SPAR. 
[From its great specific gravity, as compared with other non-metallic minerals.] 
Baryte Sulfatee. Hauy, — Sulphate of Barytes. Cleaveland and Thomson. — Prismatic Heavy Spar. Jameson. 
— Prismatischer Hal-Baryte. Mohs. —Barytes. Phillips. —Barytine. Beudant. — Heavy Spar. Shepard and 
Dana 
Description. Colour, when pure, snow white ; but it is some¬ 
times grey, black, blue, green, yellow, red and brown. It occurs 
regularly crystallized, also massive and disseminated. Primary 
form a right rhombic prism. Fig. 29. M on 1VP 101° 42b Clea¬ 
vage parallel to M and M', perfect. Fracture uneven, splintery and 
earthy. Lustre resinous or pearly, inclining to vitreous. From 
transparent to opaque. Brittle and very easily frangible. Hardness 
from 3.0 to 3.5. Specific gravity from 4.30 to 4.70. Before the 
blowpipe, it decrepitates, and is with difficulty fused into a white 
enamel. With soda, it is converted into sulphuret of barium, which, when dissolved in a dilute 
acid, gives out sulphuretted hydrogen. 
When pure, the great specific gravity will usually distinguish this mineral from others which 
it resembles. Celestine, when held for some lime in the reducing flame, and then moistened 
with a drop of muriatic acid and held to the blue part of a candle flame, colours it beautifully 
purple ; which is not the case with heavy spar. Witherite and strontianite dissolve with effer¬ 
vescence in muriatic acid, while heavy spar is not acted on by it. It is, however, in some cases 
quite difficult, without a detailed analysis, to distinguish between the salts of baryta and the 
corresponding ones of strontia. 
Fig. 29. 
