ST R
( 342 ) STR
tranfparent: the other varieties are only trans-lucent on the edges. It is confiderably hardand brittle. Sp. gr. 3.—3.3.
It is fufible before the blowpipe into a vi-treous fcoria of a black or grey colour.
Its component parts according to Bergman are64. Silex2o. Magnefia2.7 Alumine9.3 Lime4. Oxyd cf Iron
100.0
The maflive varieties occur in beds in primi-tive mountains, accompanied by galena, pyrites,and magnetic iron ore: the cryftallized varietiesoccur in dolomite, foliated talc, and in veins ofthe oldeft formation, accompanied by mica,titanium, &c. It abounds in the Tyrolefe Alps,particularly in the Zillerthal, alfo in the ItalianAlps, in Saxony, in Norway , and in fomeparts of the north of Scotland .
2. Subfp. Afbeftiform Strahlftein.
Its colours are greyifh or greenilh white,.reddifh or yellowifh white, olive green, moun-tain green, fmalt blue, and liver brown. Itoccurs in mafs, .difleminated, and fometimes inbrilliant, flexible, elaftic, capillary cryftals.Internally it is gliftening, with a pearly luftre.Its fradture is divergingly radiated, or flenderfibrous. It occurs in coarfe and wedge fliapedprifmatic diftindt concretions. It is fometimestranflucent at the edges, but more commonlyopake. It gives a greenifli white ftreak; ismoderately hard, approaching to foft j is brittlebut not very frangible. Sp. gr. 2.5 to 2.9.
It is fufible before the blowpipe without.addition into a black or grey fcoria.
It occurs at Rafchau in Saxony mixed withgreen copper ore and pyrites; in Bareuth,■mixed with ferpentine and fteatite: it alfo occursin the Bannat.
3 .Subfp. Glafly Strahlftein. Epidot, Ilauy.Acanticonhe,—Arendalite of fome authors.
Its colour is olive green, palling into graflsgreen, mountain green, and brownilh green.It occurs in mafs, or cryftallized in hexahedral•prifms, often laterally aggregated. The lurfaceof the cryftals is fmootli and brightly Alining.Internally it Is more or lefs fliining with avitreous luftre. Its fradture is between radiatedand fibrous. It occurs in flender prifmatic, orgranular diftinft concretions. Its fragmentsare fplintery and wedge fliaped. It is tranflu-cent palling to femitranfparent; is moderately
hard, very brittle, and eafily frangible. Sp.gr. 2.9—3.49- 1
The Arendalite has been analyzed by Vau-quelin, and the epidot of the Alps by CoUet.de*Cotils with the following refults.
Vauq. Coll.
37 — .37 Sile*
21 — 27 Alumine
15 — 14 Lime
24 —- ij Oxyd of Iron
1.5 — 1.5 Oxyd of Manganefe
98.5 — 96.5
It occurs in the fame fituations as the com-mon ftrahlftein; and alfo at Arendahl in Norway in veins mixed with quartz, garnets, and mag-netic iron ore.
There is a great analogy between the feveralfubfpecies of ftrahlftein, and hornblende, tre-tnoiite and albeftus.
STRONTIAN.
This alkaline earth was firft procured fromits native carbonat found at ftrontian in Argyle-fliire, whence its name. It has fince beenfound near Briftol and in various other places,combined with fulphuric acid. The pure earthmay be obtained either from the carbonat or thefulphat by the fame procefles as thofe employedin procuring pure Barytes: as the native car-bonat of ftrontian is however confiderably rarerthan the carbonat of barytes, the moft econom-ical method upon the whole of preparing pureftrontian is to mix the native fulphat of thisearth (being previoufly well levigated) withtwice its weight of cryftallized carbonat ofpotafii, and expofe the mafs to a moderate redheat for half an hour in a filver crucible, orboil it for an hour with diftilled water. Bythis procefs a double decompofition takes place,the fulphuric acid quitting the ftrontian to unitewith the potafli, while the carbonic acid of thislatter combines with the ftrontian: the mafs isnow to be wafhed with hot water till the fulphatof potafh is difiolved out, and nothing remainsbut carbonat, and probably a little undecom-pofed fulphat of ftrontian: diluted nitric acidbeing now added, nitrat of ftrontian will beContained in folution: the clear filtered liquor byevaporation and cooling will depofit the faitwhich it contains in cryftals, and thefe beingignited in a platina crucible till the acid is en-tirely decompofed and driven off, there willremain behind a fomewhat indurated mafs of agrey colour, which is pure ftrontian.
Strontian has a hot pungent acrid tafte great-ly refembling that of quicklime; when expofed