Earths. 
451 
Earths. MINER 
earbonat of lime ; many are partially occupied by mafles 
of brown clay, in which irregularly-lhaped nodules or 
blue fluor are met with. A tranfverfe fefition of ^hele 
nodules exhibits a .concentrically-cryftalline ftru&ure. 
This is the variety that is molt commonly employed in 
the fabrication of ornamental vales, &c. The natural 
colours may be modified or deftroyed by heat; palling 
from blue to reddilh purple, brown, and different Ihades 
of yellow ; in the laft change having often a honey¬ 
combed appearance ; but the colours thus artificially ob¬ 
tained never equal the natural colours in beauty. 
6. Fluor pyramidaiis, or pyramidal fluor: hardifh, 
fhining, lamellar, brittle, breaking into pyramidal, frag¬ 
ments : a, with a Angle three or fix iided. pyramid ; | 3 , 
with a double four-fided pyramid. Found in Derbyfliire, 
Devonfliire, and Cornwall ; and in various parts of 
Sweden, Saxony, and Bohemia. The colours vary as in 
the preceding. 
7. Fluor kryolitis, kryolite, or chryolite, the alumine 
fliCatee alcaline of Hairy. The colour of this mineral is 
Ynow-white, fometimes brownifh-yellow, by the admix¬ 
ture of a fmall portion of iron ochre. It occurs rnaffive, 
generally in angular fragments with faint ftrise, indicat¬ 
ing a rhomboidal nearly-cubical nucleus; fecondary forms 
have not yet been Obferved. Its luftre is vitreous, often 
inclining to pearly. Fradture imperfectly foliated, l'mooth 
in one direction, and uneven in another. It is tranllu- 
ccnt even in fragments of confiderable fize ; fmall pieces 
approach to tranfparent, and when immerfed in water for 
fome time become completely fo. It is eafily frangible. 
Specific gravity, a - 928 to Before the blow-pipe it 
foon melts, (though certainly not with fufficient eafe or 
rapidity to warrant the incorredt appellation of kryolite, 
fuppofed to be derived from that circumftance ;) and is 
afterwards converted into a white opaque pearly flag, of a 
{lightly alkaline tafte. With borax an opaque pearl is 
formed, which, fome time after cooling, {hows a degree 
of deliquefcence. It is not operated on by the muriatic 
and nitric acids, but is dilfolved by concentrated ful- 
pliuric acid under developement of greyifh-white vapours 
that corrode glal's. 
Profeffor Abildgaard, who was the firft who analyzed 
this mineral, which had before been miftaken for a fub- 
ftance related to barytes, found it to be compofed of alu¬ 
mine and fluoric acid. Vauquelin, who examined it after 
him, obtained the fame refults; and both chemifts, ac¬ 
counted for the fmall proportion of alumine which they 
found, by the pofiibility that part of the earth might have 
been carried oft' by the fulphuric acid. Klaproth was 
enabled to aflign the true caufe of the apparent difpropor- 
tion by the dilcovery of a confiderable proportion of foda, 
till then but little known as an ingredient of ftony fub- 
ftances. His analyfis, and the fubfequent one by Vau¬ 
quelin, have given the following refults : 
Klaproth. Vauquelin. 
Alumine 24. 2i"j 
Soda 36 32 >xoo parts. 
Fluoric acid and water 40 47 J 
The only place where kryolite has been hitherto found is 
Greenland ; but nothing is known relpefiting its geog- 
noftic fituation. 
Plate I. reprefents feveral fpecimens of Fluor from Mr. 
Raflileigh’s curious Cabinet of Britilh Minerals. Fig. 1. 
reprefents fluor having feveral cryftallizations varying 
in form from each other. In the centre is a large four- 
fided pyramid with a fmall cube on the point, all of a 
purple colour, and tranfparent; on the outfide is the 
figure of a very large pyramid of four lides, the outward 
furface breaking out into a number of cubical forms, with 
fiat or truncated tops, and bevilled to the edge of each 
fide the cube : thefe are all of a green colour, and tranf¬ 
parent. On the top of this pyramid is another form of a 
very peculiar fnape, but very regular, in twenty-fix fides. 
This fpecimen is from the eaft Pell-mine, in St. Agnes, 
A L O G Y. 
Cornwall. Fig. 2. a very large four-fided pyramid of 
fluor, burfting into a number of fmall cubical figures in 
every part of it, with a crofs of larger cryftals of the 
twenty-four-lided fluor on each fide the angle of the py¬ 
ramid. Thefe are all of a fine purple colour, and femi- 
tranfparent. The whole is fpotted with cubes of mundie, 
and fome blende, with a cryftal of quartz at each end : the 
top of one of the cryftals of quartz is broken; all the 
reft of the piece is perfeft. From the Pell-mine. Fig. 3. 
green tranfparent fluor, with a flat top; on each fide are in¬ 
numerable fmall cubical figures, which extend like flights 
of fteps beyond the principal figure. The fluor is nearly 
furrounded with cryftals of fix-iided quartz. Fig. 4, 5. 
two pieces of fluor, with flat tops, bevilled off to the edges 
of the cubical angles. Thefe are nearly the fame in form, 
but differ in colour. Fig. 6. reprefents a double four-fided. 
pyramid of fluor, joined bafe to bafe, very large, femi- 
tranfparent, and of a light-green colour, with fix-fided 
cryftals of quartz. From Poldice, in Gwennap. 
Apatites. See vol. i. p. 787. where the generic cha- 
rafiters are given, and a defeription of one fpecies. The 
other fpecies are as follow : 
1. Apatites rupeftris, or phofphorite: compaft, opake 
whitilh. Found at Eftramadura in Spain, forming exten- 
five ft rata with alternate ftrata of {olid quartz. It melts 
with borax into a white enamel. 
2. Apatites obtahedrus, or eight-fided apatite : in eight- 
fided tables, of a rather-greafy luftre, paralitical, breaking 
into indeterminate fragments, lemipellucid, of a minutely 
granular texture, which is lamellar when broken tranf- 
verfely. Found near Ehrenfriederfdorf in Saxony. 
3. Apatites tabularis, or fix-fided apatite: in fix-fided 
tables, of a rather-greafy luftre, parafitical, breaking into 
indeterminate fragments of a minutely-granular texture, 
which when broken tranfverely is lamellar. Habitat as 
the preceding. 
4. Apatites prifmaticus. See Apatites, as referred to 
above. 
5. Apatites chryfolithinum, or Spanifh apatite: in fix- 
fided prifms, terminated at both ends by a fix-fided pyra¬ 
mid, green, breaking into indeterminate fragments, of a 
conchaceous texture when broken tranfverfely. Found 
near Carboneira in Spain, in fmall folitary cryftals, which 
are fometimes hollow. It effervefees a little with the 
nitric acid; and emits very little, if any, phofphorefcent 
light when powdered and thrown upon burning coals; 
Specific gravity, 3‘i. 
6 . Apatites columnaris, or columnar apatite : in eight- 
fided prifms, of a rather-greafy luftre, parafitical, femi- 
pellucid, breaking into indeterminate fragments, of a mi¬ 
nutely-granular texture, which when broken tranfverfely 
is lamellar. Found near Schneeberg and Ehrenfriederf¬ 
dorf in Saxony. 
7. Apatites trihedrus, or three-fided apatite: in three- 
fided prifms, of a rather-greafy luftre,. parafitical, femi- 
pellucid, breaking into indeterminate fragments, of a 
minutely-granular texture, which when broken tranf¬ 
verfely is lamellar. Found near Ehrenfriederfdorf in 
Saxony. 
Boracites. —Confifting of earbonat of lime, a larger 
proportion of earbonat of magnefia, the greater part bo- 
racic acid, and a little alumine, (ilex, and oxyd of iron: 
hard, lamellar, lightiih, cubic: becoming eleblric by heat, 
not effervefeing with acids, crackling in the fire, and be¬ 
fore the blow-pipe contracting and melting into a yel- 
lowifli glafs. There is but one fpecies, called 
Boracites cubicus, borat of magnefia, or boracite. It is 
found at Kalkberg near Luneburg, feated in a bed of gyp- 
fum. Colour hyaline or greyifli-white, fometimes palling 
into violet or fea-green: cubes very fmall, with truncated 
edges and angles, lo that the faces of the truncated angles 
exhibit alternately hexagons anti triangles: fracture com¬ 
pact, flat, conchoidal. Contains boracic acid 68, carbo- 
nat of magnefia 13, earbonat of lime 11, lilex 1, argil 1, 
iron 6. - 
3 
Order 
