33 
Figs. 7—9.—Sulphate of Strontia, Celestine. 
The primary form is a right-rhombic prism of 104° 48 ; 
and 75° 12' Cleavage in the direction of the planes of 
the primary form, especially in that of the terminal 
planes. In other respects, it is like the sulphate of 
baryta. Truncation of the obtuse angles (Fig. 7), or of 
the obtuse and acute angles (Fig. 8) occurs, drusy aggre¬ 
gations are also found, partly with double truncation 
of the angles (Fig. 9), as well as radiated crystalline-granu¬ 
lar masses. The crystals are frequently a sky-blue, which 
is also the colour of fibrous celestine—the so-called schutzite 
of Jena and of Pennsylvania, and which has also been found 
at Aust Ferry, near Bristol. Transparent, translucent, 
friable ; hardness 3-0—3 - 5, sp. gr. 3*6—4’0. The trans¬ 
parent crystals refract the rays of light double, and have 
a bright vitreous lustre. The chemical constituents are 
simple sulphate of strontia, Sr S=56-36 of strontia, and 
43’64 of sulphuric acid, usually with traces of the oxide of 
iron, carbonate of lime, and water. There are also lime, 
and baryta celestines. It decrepitates before the blow¬ 
pipe, but not so violently as baryta, and melts to an 
enamel, reddening the flame. Insoluble in acids. The 
finest crystals are found at Girgenti in Sicily, mostly in 
native sulphur (Fig. 9) ; also in Hungary, North America; 
sometimes also with strontianite at Stuttgart, at Soluthurn, 
and Yicenza; the radiated foliated variety occurs prin¬ 
cipally in the Fassathal, the fibrous at Jena, the calca¬ 
reous at Paris, in thick crystalline masses of a greenish-grey 
colour. Celestine (Latin ccelestis sky-blue) is used prin¬ 
cipally in the preparation of nitrate of strontia, which is 
used for producing the red-fire in fireworks, for which pur¬ 
pose it is generally obtained in this country in the neigh¬ 
bourhood of Bristol, where it occurs in granular masses. 
IX. SALTS 
Pure compounds of potash are of rare occurrence in 
nature, and they are for the most part products of decom¬ 
position, sometimes by fire and volcanoes, and sometimes 
by the action of nitric acid on other minerals. They are 
thus generally double combinations, as we may have seen 
in considering the felspars. The following compounds are 
true salts, that is, combinations of acids with bases; they 
are soluble in water, and impart a violet colour to the 
flame of the blow-pipe. 
Fig. 10.— Sulphate of Potash. 
The primary form is a right-rhombic prism of 112° 8', and 
67° 52'; hexagonal double pyramids (Fig. 10) occur most 
frequently, however, with a specific gravity of 1-73, and a 
hardness of 2 - 5—3-0 ; small acicular crystals and crystalline 
masses are also found in many lavas of Vesuvius. The co¬ 
lour is white, passing into yellow, bluish, and grey. It dis¬ 
solves in five times its volume of boiling water, and has a 
brackish taste. The elements are, potash 54-75 parts, and 
sulphuric acid 45*25 parts, simple sulphate of potash — K S. 
Before the blow-pipe it melts with crepitation, and forms 
sulphuret of potassium in the inner flame, which is soluble 
in water, and blackens silver. 
Fig. 11.— Potash-Alum, Alum, Alum-Salt. 
Alum crystallises in regular octahedrons, which some¬ 
times assume a ladder-like form, like Fig. 11. Cubes also 
are found with and without truncated angles, as well as 
fibrous, capillary, and stalactitic varieties. Colour, white, 
grey, yellow. Lustre, vitreous. Translucent. Hardness 
2-0—2-5. Sp. gr. 1-75—2-0. Readily soluble in an 
equal weight of hot water, and very large crystals may be 
obtained from the solution by occasionally stirring round 
small crystals that have been introduced, and by gradually 
allowing the fluid to evaporate. The taste is a sweetish as¬ 
tringent, somewhat sour, and it has an acid re-action. The 
chemical composition is sulphate of potash with sulphate of 
OF POTASH. 
alumina, and 24 eq. of water = K S + Al S 3 + 24 H. It 
melts easily when heated, and swells up to a great extent ; 
it colours the flame violet, and is made blue by nitrate of 
cobalt. 
Potash-alum is found as a product of burning coal beds 
at Saarbriick, Duttweiler, and frequently in fine crystals, 
in the department of Aveirons in France; fibrous or efflo¬ 
rescent in the alum-shale of the Upper Palatinate, in 
Saxony, and Swabia; also at Whitby in Yorkshire, and at 
Hurlet, near Paisley, and is used for the manufacture of 
crystallised alum for dyeing, and other purposes. Alum is, 
however, principally prepared from alum-stone, from the 
bituminous clay-slates of the stratified formations impreg¬ 
nated with pyrites, and partly, too, as an after-product in 
the manufacture of green vitriol (sulphate of iron), etc. 
Alum-stone occurs in thick masses, and in obtuse 
rhombohedrons of 5'0 hardness, and 2-67—2*69 sp. gr. 
It is a triple-sulphate of alumina, consisting of 12 eq. of 
alumina, with 1 of simple sulphate of potash, and 8 eq. of 
water. Insoluble by itself in water, when heated and 
lixiviated with water it gives the Roman alum which used 
to appear in commerce in small dim octahedrons, and on 
account of its purity, was principally employed for scarlet 
dyes. The best were prepared at Tolfa, in the Papal 
States, from the rough alum-stone found there; latterly, 
however, it has been found in great masses in Hungary 
and Siberia. 
There are also soda, ammoniacal, manganese, magnesia, 
and iron alums, in which these bases take the part of the 
potash, and most of them, owing to the alumina which 
they contain, are also applicable to dyeing. The feder- 
alum (feather alum) is a tolerably pure iron-alum, which 
occurs in asbestus-like needles, of a yellowish colour, prin¬ 
cipally as an efflorescence in many alum-shales. This 
shale is nothing else than bituminous clay-schists, inter¬ 
spersed with sulphate of iron, which is readily decomposed 
by the atmosphere, especially if it has first been slightly 
heated, and it occurs in the neighbourhood of many stone 
and brown coals, particularly also in the lias formation, 
and often in considerable quantity. 
