TRI
TUN
( 442 )
land, in the Tyrol, Tranfylvania, Moravia , andat Langenfeldt in Saxony; alfo in Siberia nearLake Baikal , in the Shetland iflands, and in thecaftle rock of Edinburgh .
It occurs principally in primitive mountains,imbedded in dolomite or granular limeftone, andmixed with mica and talc. It is alfo found inthe fecondary trap-formation, accompanied byprehnite.
TRIPHANE. Spodumene , D’Andrada andWerner.
Its colour is apple-green, or greenilh-white.It occurs in mafs. Its longitudinal frafture is{hilling, its crofs fradture is gliltening, witha pearly luftre. Its fracture is foliated in twodirections; the crofs fradture is fine graineduneven. The fragments are indeterminate, orin the form of very oblique rhombs. It istranflucent, moderately hard, and eafily frangi-ble. Sp. gr. 3.21.
Before the blowpipe it becomes yellow andfplits into thin plates, and then melts into atranfparent greyifh glafs.
It has hitherto been found only in the minesof Uton, near Dalero in Sweden , in veins withquartz and back mica.
Its colour is yeliowifli-grey, palling into afh-grey and reddilh-brown. It occurs in mafs,and is without luftre; its frafture is coarfe-grained earthy, palling into obfcurely flaty. Itis foft, often friable; is meagre and rough tothe touch, and does not adhere to the tongue.
It is fcarcely fufible before the blowpipewithout the alliftance of borax. It is com-pofed, according to M. Haafe, of90 Silex7 Alumine3 Oxyd of iron
100
It was formerly brought to Europe fromTripoli in Africa , but has fince been found inSaxony , at Pottfchappel near Drefden, in Der-fjyffiire, in Flanders, Switzerland , Hefle, Weft-phalia and Ruftia. It occurs in veins and bedsin fecondary rocks, and probably fometimes isa pfeudo-volcanic production.
It is largely employed in polilhing metals,marble, glafs, and other hard bodies.
TUBE OF SAFETY.
An article of chemical apparatus, for an ac-count of which fee the Appendix .
TUFA calcareous. Kalk Tuff, Wern.
Its colour is yellowilh-grey 0 r fmoke-grey.It occurs fometimes folid, but generally porousand marked with impreffions of reeds, mofs,and other vegetables. Its luftre, when it haSany, is faintly glimmering. Its fracture is finegrained uneven, palling into earthy. It is foft,eafily frangible, and not much heavier thanwater.
It effervefces with acids, and is little elfe thancarbonat of lime.
It occurs in alluvial land, being depofited bywater impregnated with carbonat of lime.
The more compact kind* are employed inbuilding, for which their lightnefs well adaptsthem.
TUNGSTEN. Scheelium.
Tungften is a hard brittle granular metal,very difficultly foluble in the acids, combine*with the alkalies, and is converted from yellowto blue oxyd by muriated tin.
$. 1. Ores.
Sp. 1. Tungsten. Schwerjlein, Wern.—Scheelin calcaire, Hauy. Goffan , of the Cornilhminers.
Its colour is greyifh or yellowiffi-white,palling into yellowilh-grey; it is often fuper-ficially tarnilhed to dark pearl-grey or yellowifhbrown. It occurs in mafs, diffeminated, andcryftallized. Its primitive form, according toHauy, is the cube; but the ufual form that itprefents is the odtohedron, either regular, orbevilled at the common bafe of the pyramids, orcuneiform. Its cryftals are middle-fized orfinal]. The lateral planes of the cryftals arefmooth and brightly fhining with a nearly ada-mantine luftre. Its fradture is imperfectlyfoliated, palling into conchoidal and uneven ;that of the mailive varieties is granular andfplintery. It fometimes occurs in large or fmallgrained diftinct concretions. The cryftallizedis tranflucent, rarely tranfparent; the mailive isopake. It maybe fcraped without difficulty bya knife, is eafily frangible, but not particularlybrittle. Sp. gr. 6.ei. = 5 - 57 -
Before the blowpipe, without addition, itcrackles and becomes opake, but is not fufible.When pulverized and digefted with nitric ormuriatic acid it leaves a lemon-yellow refidue,which is tunftic oxyd. This mineral has beenanalyfed, firft by Scheele, then by the Elhuyars,and laltiy by Klaproth , with the followingrefults.