454 Earths. MIN E R A L O G ?. Earths. 
14. Argilla cimolia, or cimolite : pearl-grey, becoming 
reddilh when expofed to the air, adhering ftrongly to the 
tongue, not llaining, becoming white before the blow¬ 
pipe. Found in the ifle of Argentiers, in the Archipe¬ 
lago, where it is ufed for whitening fluffs: texture earthy, 
fra 61 ure uneven; opake, foft, breaking with difficulty. 
Specific gravity 2. Contains filex 63, alumine 23, iron 
1-z 5, water 12. Klaproth. 
15,. Argilla Sinenlis, or Chinefe clay: rather meagre 
to the touch : rufous, variegated with ochraceous dots 
and fpots ; foftening in water. Found near Montmartre 
in France, and in China, where it conllitutes the foil 
upon which cotton, rice, and indigo, are cultivated: it 
is ufed in the making of bricks which arc intended to be 
under water. 
16. Argilla rubrica, or red ochre: foft, llaining, ad¬ 
hering to the tongue, red, brittle, does not become duc¬ 
tile in water, of an earthy texture. The term ochre, in 
its original acceptation, implied a yellow earth ; for Theo- 
phraftus, having already called it an earth, lays that it is 
ufed inllead of arfenic; and Pliny fays of arfenic, that it 
is mod valuable when of a pure golden colour. Nume¬ 
rous paffages might be produced, were it neceffary, to 
prove this point. The term is at prefent applicable to 
any coloured earth ; but particularly to natural clays co¬ 
loured by oxyd of iron. The principal varieties are yel¬ 
low, red, and brown. The red is found in Siberia, Dale- 
carlia, Bohemia, Portugal, and France, generally among 
iron ore, with which it commonly abounds. Colour dark 
red, or intermediate between brick and blood-red. Frac¬ 
ture earthy, iometimes conchoidal: feels rough, afi'umes 
a polifli from the nail, ftrongly ftains the fingers, adheres 
to the tongue, falls immediately to pow'der in water, does 
not effervefce nor eafily diflolve in acids, crackles and 
grows black when heated to rednels, and melts atlaft 
into a dark greenifh-yellow frothy enamel. 
17. Argilla lutea, or yellow ochre: very foft, llaining 
the fingers, and adhering to the tongue. Found near 
Wehrau: feels fmooth or fomewhat greafy: fra6lure 
earthy, or inclining to the conchoidal: adheres ftrongly 
to the tongue, takes a high polifli from the nail, and 
ftrongly ftains the fingers: falls immediately to pieces in 
water, with fome hilling, afterwards to powder, but does 
not diffufe itfelf through it: does not effervefce with 
acids, or eafily diflolve in them: heated to rednefs it 
crackles, hardens, acquires a red colour, and gives a red- 
difti ftreak, and melts at laft into a liver-browm porcelain 
mafs : contains alumine 50, oxyd of iron 40, water acidu¬ 
lated by fulphuric acid 10. This fubftance is principally 
made ule of as a coarfe paint. A variety met with in 
Shotover-hill, near Oxford, is of a remarkably uniform 
colour and fine texture ; it is preferred in commerce to 
all others. Coarfe yellow ochre is frequently converted 
into red ochre by calcination; in which procels probably 
the carbonic acid or fixed air is driven off', and the iron 
at the fame time is further oxydated by means of the de- 
compolition of the moifture contained originally in the 
ochre. Theophraftus fays that the method of condu6ling 
the procels was accidentally difeovered by a perfon, who, 
in an inn which had been burnt down, faw a heap of 
ochre that had been partly changed to a red colour by 
the a6tion of the fire. 
18. Argilla viridis, or green bole : a little greafy ; foft, 
compa6l, green; lwelling in the fire, and becoming firft 
blackilh, then red, and at laft yellow. Found on Mount 
Baldo, Sweden, Normandy, Saxony, and Bohemia, fre¬ 
quently within the almond-ftone: makes a green mark. 
19. Argilla Tripolitana, or Tripoli. This fubftance 
was originally fo called from the town of the fame name 
in Barbary, whence it was commonly imported: but the 
name has been extended to fimilar fubftances in different 
•parts of the world. The opinions refpedting its nature 
are various; lome l’uppofing it to have arilen from the 
decompoiition of porphyry orjafper; others, from bafal- 
fcic rocks. Saufture conje6lure& that it is a very fine land 
waffled and depofited by water; and Wallerius deferibes 
it as a kind ot fine fand-ftone. Any filiceous fubftance 
reduced to a fufliciently-minute Hate of divifion may be 
ufed inllead of, and hence is often called, tripoli: this is 
the cafe with the rotten-ftone of Derbyffiire. It is fome- 
times imitated by calcining and reducing to powder cer¬ 
tain varieties of flate. 
The fpecific charafters, as given by Gmelin, are—harfft 
and dry, foft, lightilh, adhering to the tongue, melting 
with difficulty, when rubbed with metal affuming a me- 
talic fplendour. It is found in the ifland of Tanna in 
the South Seas, in the kingdom of Tunis, in Naples, at 
the river Uda in Ruffia, Sweden, Flanders, Bohemia, 
Aullria, and various parts of Germany, in ftratified 
mountains, and not unfrequently mixed with fulphur. 
Colour whitilh, yellowilh-grey, cream and ochre yellow. 
It is found folid, has a dull earthy appearance when 
broken, and breaks into indeterminate obtufe regular 
pieces; is foft and fandy between the teeth, and abforbs 
water with a noife : does not ltain the fingers, and fre¬ 
quently reddens when heated. Contains filex 90, alu¬ 
mine 7, iron 3. 
20. Argilla tumefeens, or bog-clay: reddening a little 
when heated, fpongy when dry ; greedily imbibing water 
with intumefcence, and retaining it. Found every-where 
in barren places, particularly in Sweden ; and on account 
of its fludluation and trembling is very dangerous to tra¬ 
vellers ; for the furface being dried up is elaftic like lea¬ 
ther, while the mafs under it is of the confidence of 
poultice. 
21. Argilla grandasva, or hard clay: meagre, fomewhat 
plaftic, growing reddilh and hardening in the fire, friable, 
and a little dully when dry, (lowly imbibing water with 
intumefcence. Found in Sweden, particularly in Dale- 
carlia ; grey, brown, or reddilh, and in the fummer be¬ 
comes fo hardened as not to be broken by a hammer or 
divided by a wedge: when fifted, it is an excellent mate¬ 
rial in the formation of bakers’ ovens. 
22. Argilla foluta, or foluble clay: fomewhat meagre, 
a little plaftic when moillened, dulty when dry, melting 
into folid glafs in the fire. Found ill Sweden, chiefly un¬ 
der bogs and marlhes; grey or white; the latter is ufed 
for whitening walls. 
23. Argilla arvenfis, or field-clay : cinereous; forming 
fmall clods when moillened, fplitting into large clefts 
while drying, and becoming at laft powdery ; vitrifying 
in the fire. Found every-where in cultivated lands. 
24. Argilla umbra, brown ochre, or umber: penetrated 
with bitumen, brown, making a mark, growing reddifli 
when burnt. Found in Britain, Umbra in Italy, in Ger¬ 
many, &c. and is ufed by painters. Colour browm or 
blackilh; adheres to the tongue, and moderately ftains 
the fingers. Conlilts principally of particles of decayed 
wood mixed with bitumen. 
25. Argilla vitriolacea, or vitriolated clay: brown, 
ftyptic, turning a decodtion of galls black. Found every¬ 
where under boggy land ; and is a mixture of clay and 
pyrites. 
26. Argilla falfa, or faline clay : of a lh.lt tafte. Found 
in the maritime parts of Aullria,^ and in the confines of 
falt-pits ; cinereous or red, and is impregnated with mu- 
riat of l'oda. 
27. Argiila cobaltifera, or cobalt-clay : black, forming 
a blue glafs when melted with borax. F'ound in the 
mines of Wirtemburg. 
28. Argilla cuprifera, or cupreous clay: brown, pro¬ 
ducing a blue colour with heated fpirit of ammonia. 
Found in the mines of Germany; contains the oxyds of 
iron and copper, in the proportion of about 26 per cent, 
of the latter. 
29. Argilla argentifera, or filvery clay: foft, plaftic, 
exhibiting filver when ful'ed wdth lead. Found near 
Crierldorf in Bavaria, and near Schemnitz in Hungary; 
cinereous, yellowilh, or yellow-red ; contains - oi of filver. 
50. Argilla aurifera, or auriferous clay: foft, plaftic, 
bluifh, 
