Metals; MINERALOGY. Metals. 
516 
in having its cryftals in an elongated odtohedron, wlicfe 
bafe is a fquare, with the fummits complete or truncated, 
and the faces tranfverfely ftriate. Colour fteel-grey, ver¬ 
ging to black or deep blue; luftre vitreous, generally 
opake. Specific gravity, 3• 8 57. 
4. Titanium nigrina, nigrine titanite, or fphene : com- 
padt, hard, brittle, with a waxy luftre and foliated texture, 
imperfectly foluble in muriatic acid, from which it p.reci- 
-pitates a clammy yellowifii mafs with the addition of am¬ 
moniac. Found near Paflau in Bavaria, at Arendal in 
Norway, and near St. Gothard ; fometimes maffive or dif- 
feminated, fometimes cryftallized in fiiort obtufangled 
four-fided prifms. Colour reddifh, yellovviih, or blackifh 
brown, rarely whitilh-grey, with a whitilh-grey powder. 
Before the blowpipe it is infulible, but in charcoal it is 
converted into a black opake porous flag. Specific gra¬ 
vity, 3-5. Contains oxyd of titanium 33, iilex 35, lime 3 3. 
The name of fphene is given to this mineral by Haiiy, 
from the wedge-like fliape of fome of its cryftals. 
( 3 . Foliated fphene differs from the above in colour, 
which is various fliades of yellow, inclining to a ftraw or 
cream colour, and in the ftrudture, which is foliated, with 
a double cleavage parallel to the fide of an oblique four- 
fided prifm. The crofs-fradture is foliated. Both thefe 
varieties of fphene pafs from different degrees of tranflu- 
cency to opacity. 
Chromium, Chrome.— Generic charadters : White 
-with a fhade of yellow, very brittle; very difficult of fu- 
fion ; gradually oxydating in the nitric acid, and the oxyd 
becoming green when heated in a dole veil'd. 
1. Chromium plumbi, chromat of lehd, or red-lead ore 
of Siberia: red with a fhade of yellow', and a fine orange- 
yellow ftreak and powder ; texture compadt, cryftallized. 
in four-fided prifms ; a condudtor of the eledtric fluid. 
This is the fubftance in which the metal was firft difeo- 
vered. Chromat of lead was originally met with in a 
mine fituated on the eaftern ridge of the Ural mountains, 
in Siberia, in about the fifty^-third degree of north lati¬ 
tude. It occurred, in diftind cryftals, in a vein running 
in gneifs or micaceous fchiftus : the principal vein of the 
mine was worked for the fake of the gold it afforded, 
which is contained in a liver-coloured iron-ore, of a cubic 
form. Since that time it has been dil'covered in the fame 
neighbourhood, in the form of a thin irregular incrufta- 
tion, on a kind of ochry micaceous fchiftus; and all'o, in 
a cryftalline form, in the interftices of a ftratified land- 
ftone. In Ruffia it is much ufed in oil-painting, and is 
very highly valued on account of its durability. Chromat 
of lead is diftinguiflied from realgar, which often clofely 
refembles it in colour, by not emitting a fmell of garlic 
upon the application of the blowpipe; from red filver, by 
the yellow tinge of its powder; from cinnabar, or ful- 
phuret of quickfilver, by the fame mark ; befides which, 
cinnabar is entirely volatilized by the adion of the blow¬ 
pipe, whereas chromat of lead is reduced to a metallic 
ftate. Chromat of lead is fometimes fuperficially co¬ 
vered with a pulverulent or minutely-cryftallized fub¬ 
ftance, of a green colour. This is a combination of oxyd 
of lead with oxyd of chrome ; and may by the eye be 
miftaken for phofphat of lead, or green carbonat of cop¬ 
per ; but, if thrown into nitric acid, it communicates to 
the liquid an orange red colour ; and may thus be diftin- 
guiflred from both thofe fubftances. Specific gravity, 6. 
Contains oxyd of lead 65-12, chromic acid 34-88. 
2. Chromium ferri, or chromat of iron : brown, with 
an alhy-grey powder and flight metallic luftre; melted 
with potaih, and dilfolved in water, imparting an orange- 
yellow colour to the folution. Found near Caflin (de¬ 
partment of the Var) in France, and in Siberia, in irregu¬ 
lar mafles. Colour reiembling that of brown blende ; 
hardnefs fufficient to fcratch glafs; infoluble in nitric 
acid, but melts with borax into a fine green glafs. Spe¬ 
cific gravity, 4. Contains chromic acid 43, oxyd of iron 
24'7, alumine 20-3, filex 2. 
In the year 1799 there was difeovered by M. Poutier, in 
the department of the Var, near la Baftide de la Caffade, 
a new mineral, which, on analyfis, firft by M. Taflaert, 
and afterwards by M. Vauquelin, proved to be chromate 
ot iron. Since that time, M. Meder has difeovered, in 
the Uralian mountains in Siberia, a mineral, the external 
charadters of which prefent a ftriking analogy with thofe 
of the French chromate of iron. It has been analyfed in 
an elaborate manner by M. Laugier, and appears to confift 
of chrome 53, iron 34, alumine 11, filex 1. In the Ann. 
de Chimie, 1811, M. Laugier enquires whether the chrome 
in this mineral, and in the French one, exifts in the ftate 
of oxyd or of acid ? and is inclined to adopt the former 
opinion ; in which cafe, the fubftance is not to be confi- 
dered as a compound metallic fait, but as an intimate 
mixture, pfcrhaps a combination, of two metallic oxyds. 
3. Chromium nativum, or native oxyd of chrome. 
The department of the Saone and Loire has already fur- 
111 ihed feveral interefting minerals. The titanium of 
Gourdon, the oxyd of uranium of St. Symphorien, the 
graphic granite and the aqua-marines of Marmagne, are 
among the recent treafures difeovered in this diftridt. 
To thefe is now added by M. Lefchevin, a fubftance, 
which, if obtainable in fufficient abundance, may prove 
of very material importance to the manufadtories of por¬ 
celain and of coloured glafs in the French empire. The 
hill of Ecouchets, midway between Creuzot and Couches, 
confifts of breccia and fandftone, compofed of fragments 
of granite, and of other primitive rocks, cemented toge¬ 
ther by quartz and coarfe chalcedony, which alfo not un- 
frequently form fmall veins in the fandftone. Some of 
thefe veins are of a beautiful mountain-green colour, 
which has occafioned feveral perfons to fufpedt the pre¬ 
fence of copper; and allays, though uniformly unluccef- 
ful, have been frequently undertaken, for the purpofe of 
difeovering the prefence of this metal. The fpecimens 
the richeft in colouring matter, communicate an intenfe 
and rich emerald-green to borax. Their natural colour 
is a bright apple-green ; the fpecific gravity varies from 
2-57 to 2-61 : they are rough and dry to the touch, and 
are of an earthy uneven fradture. M. Drapiez has made 
two analyfes of this mineral with the following refults; 
Silex - 64- 52" 
Alumine - - 23- 27* 
Lime and magnefia 2-5 4-5 
Oxyd of iron a trace 2- 
-of chrome - 10-5 . 13- 
ioo-o nS c 5 JournaldePhyfique , 
— —— t May 1810. 
COLUMBiUM,Columbite.—Generic characters: Brown - 
ifh-black, internally iron-grey, with a chocolate-brown 
ftreak and powder ; hardifh, very brittle, of an imperfedt- 
ly-foliated texture, opake, not attradled by the magnet. 
Specific gravity, 5-9. 
Columbium compabtum, or tolumbite. Sent to fir 
Hans Sloane from Maflachufetts; and is at prefent in the 
Britifh Mufeum. Colour dark grey-brown, with a glaffy 
luftre ; rather hard, and very brittle : longitudinal frac¬ 
ture imperfebtly lamellar, crofs-fradture fine-grained: 
when expofed to a violent heat for a long time, was found 
in a ftate of black powder. Contains oxyd of colum¬ 
bium 78, oxyd of iron 21. 
Tantalium, Tantalite.—Generic charadters : Black- 
ifli-grey, foftilh, of a granular fradture, not magnetic; 
fpecific gravity, 6-5 ; not foluble in any acid, nor alter¬ 
ing its colour when heated to rednels; melting with 
phofphat of foda and borax into a colourlels glafs. There 
are two fpecies. 
1. Tantalium magnefiatum, or tantalite: confifting of 
oxyd of tantalium combined with the oxyds of iron and 
manganele. Found at Kimito in Finland, in irregular 
cryftals. Colour between bluifti-grey and blackifti-grey ; 
furface fmooth with metallic luftre 5 very hard ; fradture 
compadt. Specific gravity, 7-953. 
2. Tan- 
