mentioned. It is applicable to an infinite varietyof purpofes, is eafily wrought by calling and.hammering, and by the lathe, its wire is emi-nently ufeful, and it takes a high and very beau-tiful polilh. The appearance of brafs is givento other metals by walhing them with a yellowlacquer or Varnish, a fubftitution often verymuch to the detriment of the manufacturedarticle.
Many other yellow alloys of copper are ufed,fuch as bronze, bell-metal, &c. moll of whichare triple compounds, and will be noticed underthe article Copper .
BRAUNSPATH. 1 Pearl-fpar. Sidero-calciteof Kir wan. Spath bruniflant of Brochant. Chauxcarbonateeferrifere Hauy.
The colour of this mineral is milk-white,palling into greyifh, yellowilh or reddilh-white;or rofe-red palling into flefb, blood, or brownilh-red: when it has been expofed for fome timeto the action of the weather it becomes lirll ofa yellowifh grey colour, and then verges intoochre or Ifabella-yellow, yellowilh, reddifh, liverand blackifh-brown. It is fometimes fpotted,an accident that happens moll frequently withthe red-coloured varieties.
It occurs generally cryftallized, and the formsof its cryftals that are determinable are thefame as certain varieties of calcareous fpar. Itsprimitive figure is a rhomboid exactly corref-ponding with that of calcareous fpar. The otherfigures are,
1. Equiaxe (of Hauy); a very obtufe rhom-boid.
2. Inverfe (of Hauy); an acute rhomboid,which is the primitive figure inverted.
3. Contraftante (of Hauy); a Hill more acuterhomboid than the preceding.
4. Bafee (of Hauy) •, the primitive rhomboid,the two iummits ot which are intercepted bytwo triangular facets.
5. Dihexaedre (of Hauy); an oblique fix-fided pyramid, the alternate angles of whichare equal.
The undeterminable forms of this mineralare,
6. Lenticular (lenticulaire of Hauy); which•differs from the equiaxe in having the faces and-angles rounded.
7. Curvilinear rhomboid (contourr.ee ofHauy); a fmall rhomboid, all the faces of whichform a fold in the direction of their oblique
diagonal. ...
It alfo occurs'in minute interlaced rhomboidalfcales, fome of which have a confiderable refem-
■ JEmmerling, Kinvan, Hauy, Brochant, Jan
blance to blende ; or in globular mafles or cel-lular.
The furface of the cryftals is generally drufy,except of the rhombs, which are fmooth. Itsexternal luftre is more or lefs fhining, with apearly luftre, but when in a ftate of commencingdecompofition it has ufually a variegated femi-metallic appearance. The fracture of braunf-path is ftrait or curved-foliated, exhibiting athreefold obliquely interfering cleavage, likecalcareous fpar. It flies when broken intorhomboidal fragments. It is tranflucent on theedges, rarely entirely tranflucent. Its hardnefsis a little fuperior to that of calcareous-fpar.Sp. gr. 2.83, according to Briflon; the Ilabellayellow variety, according to Kirwan =2.39.
Before the blowpipe braunfpath crackles andfalls to pieces, and becomes of a brownifh blackcolour (hence its name) but does not melt:with borax it runs into a frothy flag. By ex-pofure to a long continued high heat in a char-coal crucible, it becomes a dark brown friablemafs, ftudded with minute metallic grains; ina clay crucible It produces a brown glafs, traaf-lucid on the edges and tranfparent in thinfhivers. b It eftervefces with acids, thoughfeebly, and not except it is pulverized.
The maffive variety, when calcined and mixedwith fand forms a ftrong and valuable cement,which fets quickly and is impenetrable by water.
The conftitucnt parts of braunfpath, accord-ing to Bergman, are
50 carbonat of lime,
22 oxyd of iron,
28 oxyd of manganefe.
100
But a fpecimen that was analyfed by Berthollef,at the defire of Hauy, contained only about 4per cent, iron and manganefe, the reft beingcarbonat of lime. On this account, and becaufeits cryftallographical characters agree with thofeof calcareous fpar, M. Hauy combines thewhite or fpathofe iron ore with braunfpath underthe name Chaux carbonatee ferrifere, and ranksit as a family of calcareous fpar.
Many of the calcareous fpars which areefteemed pure, appear when analyfed by nitrousacid to contain iron ; and perhaps a regular pro-grelfion may exift from calcareous fpar with thefmalleft quantity of iron, to braunfpath, andfinally to fpathofe iron ore, or carbonat of ironwith the finalleft quantity of calcareous fpar.This however is as yet by no means afeertained,