VII. COMPOUNDS OP BARYTA. 
Baryta is the heaviest of all the oxides of the metals 
of the alkalis; hence its name, which is derived from the 
Greek B apu$ } heavy. Its combinations are not numerous; 
in general they are colourless, 3-6—4*87 specific gravity, 
hardness from 3*0—3*5, and in comparison with com¬ 
pounds of chalk they are found more sparingly, and prin¬ 
cipally in veins. They colour the blue flame of the blow¬ 
pipe greenish-yellow, and do not tarnish the charcoal, 
whereby they are essentially distinguished from the similar 
compounds of lime and lead. 
Fig. 3.—Witherite, Carbonate op Baryta. 
The primary form is a right rhombic prism (Fig. 4) of 
118° 30' and 61° 30'; the prism may be split in the 
direction of the primary planes, and in that of the trun¬ 
cated planes of the acute lateral edges, so that a hexagonal 
prism is formed. The most frequent form is a hexagonal 
pyramid, united to a second double pyramid arising from 
further truncation of the basal edges (Fig. 3). Spear¬ 
like, radiated, and compact forms also occur, as with arra- 
gonite (Plate X. Fig. 3). Generally colourless, translu¬ 
cent, lustre vitreous to fatty, friable. Hardness, 3-0— 
3-6. Specific gravity, 4*2—4*4. Soluble in acids with 
effervescence. Constitution ; simple carbonate of baryta, 
= Ba C; the carbonic acid is given off by heating, leav¬ 
ing 79*66 of oxide of barium, which is soluble in pure 
water, gives an alkaline reaction, and becomes clouded by 
the addition of sulphates. The solution in hydrochloric 
acid does not change the alcoholic flame. It melts before 
the blow-pipe to a white bead, burns and colours the flame to 
a yellowish-green. Is found in Salzburg, Hungary, Styria, 
and in especially fine crystals in England and Scotland. 
Its use is limited to the preparation of the different 
salts of baryta and chemical re-agents ; the powder serves 
for the destruction of rats and mice, and it is poisonous to 
warm-blooded animals. It has also been employed in this 
country in the manufacture of plate-glass, and in France 
in the preparation of beet-root sugar. 
Figs. 4—6.—Heavy Spar, Sulphate of Baryta. 
Also right-rhombic, the angles of the lateral edges 
= 101° 42' and 78° 18'. Cleavage in the direction of the 
planes of the rhombic prism, most easy in that of the 
terminal planes. This primary form is found very fre¬ 
quently, mostly in low tables like Fig. 4; sometimes, 
however, with truncation of the acute or of the obtuse 
angles, or also with truncation of all the basal edges, as in 
Fig. 5. The horizontal prism (Fig. 6) originates in exten¬ 
sive truncation of the obtuse angles by themselves. It 
very frequently occurs in coarsely foliated masses; it is 
more rarely earthy or mealy, and, most seldom of all, com¬ 
pact and finely granular; the radiated baryta or Bolognese- 
sjpar presents the peculiarity of phosphorescence in the dark 
after a long exposure to the sun. It is found at Bologna. 
The colour is generally white, passing into grey. It is 
friable, of vitreous lustre, translucent, of 3*6—3*5 hardness, 
and 4*17—4.487 specific gravity. The elements are simple 
sulphate of baryta, Ba S, with 65*63 of oxide of barium, 
and 34*37 of sulphuric acid. 
Insoluble in water and acids ; decrepitates before the 
blow-pipe, phosphoresces with greenish light, melts some¬ 
what more easily than felspar to a white enamel, and in 
the inner flame becomes changed into sulphuret of barium, 
which, on a piece of silver wetted with water, leaves a black 
stain, and sulphuretted hydrogen is given off. The test 
dissolves with the same phenomena in hydrochloric acid; 
the solution gives with sulphates a white precipitate, which 
is insoluble in nitric acid. The crystallised barytes occurs 
in Hungary, Bohemia, at Klausthal, at the Schwarzwald, 
etc., and the conchoidal foliated varieties in veins of the 
primary and stratified rocks, along with silver, iron, cop¬ 
per, and cobalt ores. When it is found pure white, 
in large masses, it is ground fine and mixed with white 
lead, for the purpose of lowering the price. It is also used 
in the preparation of other salts of baryta, from which 
partially pulverulent sulphate of baryta is made, and this 
is used as a colour for paint. 
The baryto-calcite and alstonite are combinations of 
carbonate of lime and carbonate of baryta in different 
proportions, which occur at Alston Moor, Cumberland. 
The sulphato-carbonate of barytes occurs at Brownley 
Hill in Cumberland, and at Dalton Fells, Westmore¬ 
land. 
VIII.—COMPOUNDS OF STRONTIA. 
Strontium is a yellowish white metal, of 2*54 specific 
gravity, and its oxide, strontia, forms the principal element 
in these minerals. Generally speaking, they resemble the 
baryta compounds; they have, however, a lower specific 
gravity (3*5—4), and they colour the blue flame of the 
blow-pipe a bright purple red. 
Strontiamte, or carbonate of strontia, has for its pri¬ 
mary form a right rhombic prism of 117° 32' and 62° 28', 
and occurs like carbonate of baryta in hexagonal pyramids 
(Fig. 3), and in spear-like acicular crystals, like arra- 
gonite (Plate X., Fig. 3), with a hardness of 3*5, and a 
specific gravity of 3*6—3*8. The chemical constitution is 
simple carbonate of strontia—Sr C. When" reduced to 
powder, it gives on live charcoal a reddish lustre. Before 
the blow-pipe, it swells up and colours the flame red without 
melting. In acids, it dissolves with effervescence. It is 
found sparingly at Strontian, in Argyllshire, at Salzburg, 
Braunsdorf in Saxony, and sometimes also in the ammo¬ 
nites (ammonitus angulatus ) of the lower lias near Stug- 
gart. 
