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S I L

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It is a fubftance of rare occurrence, havingbeen found only in a mine in the valley ofShapbach in the Black Foreft. It is accompa-nied by quartz, hornftone, and copper pyrites.

Sp. io. White filver ore. Weiffgultigerz,Wern . Mine d’argent blanche. Brock.

Its colour is light lead-grey, paffing fome-times to fteel-grey. It occurs in mafs and dif-feminated. Internally it has a gliftening me-tallic luftre. Its fracture is even, paffing intofine-grained uneven; when this latter is thecafe it is generally in a ftate of tranfition to thebrittle fulphurated filver (Sp. 8) fometimes ithas a tendency to the fibrous texture, and ap-pears to be paffing into plumofe antimony. Itgives a Ihining ftreak; is foft, not very brittle;eafily frangible. Sp. gr. 5.32.

Before the blowpipe it in part evaporates,leaving on the charcoal a filver bead furroundedwith yellow powder. Both the light and darkcoloured varieties have been analyfed by Klap-roth with the following refults:

Dark

41. Lead9.25 Silver21.5 Antimony1.75 Iron22. Sulphur1. Alumine0.75 Silex

97 <2 5

It is procured from the mine Himmelfurftnear Freyberg, where it occurs in veins ac-companied by galena, red filver, brittle ful-phurated filver, plumofe antimony, brown fpar,ai d calcareous fpar.

Sp. ix. Grey filver ore. Graugultigerz.Klapr.

This fpecies has lately been introduced byKlaproth among the filver ores as differing ef-fentially from the white filver ore with whichit is confounded by the Hungarian miners.It occurs in mafs or diffeminated through whitequartz at Kremnitz in Hungary , and appears tobe only a variety of Fahlerz or grey copper.It confifts, according to Klaproth , of,

14.97 Silver31.36 Copper34.09 Antimony3.3 Iron11.5 Sulphur0.3 Alumine

95.52

Light48.06. 20.47.882.25

. I2,2 57 -

0.25

98.09

Sp. 12. Black filver ore. Schwarzgultigerz.Wern.

Its colour is iron-black, paffing into fteel-grey. It occurs maffive, diffeminated, andcryftallized in trihedral pyramids bevilled onthe edges and folid angles. The cryftals aremiddle-fized and fmall. Internally it is fhiningwith a metallic luftre. Its frafture is fmallconchoidal paffing into uneven. It is moderatelyhard, brittle, and eafily frangible.

It has not been analyfed, and appears to be amere variety of the preceding.

Sp. 13. Sooty filver ore. Silberfchwarze.Wern. Argent noir. Brock.

Its colour is bluilh-black paffing into lead-grey. It occurs in mafs, diffeminated, carious,fuperficial or in rounded pieces. Its confidenceis between folid and friable. It is dull but ac-quires a metallic luftre by friftion. It ftainsin a flight degree, is foft, and fomewhat mal-leable.

When expofed to the blowpipe it meltseafily inco a flag, and by continuing the heat aportion is volatilized and there remains behinda dull looking globule of filver.

It has not been analyzed but is fuppofed tobe a mixture of fulphurated and horn filver ina ftate of femi-decompofition.

It occurs in veins accompanied by heavyfpar, native, fulphurated, and horn filver ores,iron ochre, malachite, and galena. It is metwith at Schemnitz and Kremnitz in Hungary ,Joachimfthal in Bohemia, Freyberg in Saxony ,and Allemont in France .

§. 2. Ajfay and Analyfis of Ores ;

The Ajfay of thefe. ores having in view merelyto afcertain the proportion of filver which theycontain, is generally conducted in the dry way.For this purpofe the ore being roafted andpulverized is to be mixed with litharge, in pro-portion to the earthy contents of the ore, andhaftily vitrified; the mafs thus produced beingpulverized and mixed with black flux is to befufed in a crucible with a fufficient heat; theconfequence will be that the lead of the li-tharge being revived will col left in a button atthe bottom of the crucible, carrying with it thewhole of the filver with fome of the other me-tals that may happen to be prefent; this buttontogether with fuch a quantity of pure lead asmay be requifite, is to be fubjefted to cupella-tion, by which all the bafe metals are fcorified,the filver remaining behind in a ftate of purity,or at moft only combined with the gold whichmany of the ores of filver contain in a fmallproportion, and which may be feparated from it