Earths. 
MINER 
Italians oecTii di gatti; but that they are not the true cat’s 
eye, which we have already feen is a fpecies of felfpar. 
13. Chalcedonius ftillatitius, or ftaladitical chalcedony : 
precipitated from water highly charged with its particles. 
Found in the Feroe Iflands, Iceland, Bohemia, Saxony, 
and many other parts of the continent; texture fometimes 
approaching to the fibrous. 
14. Chalcedonius cryftallinus,orcryftalline chalcedony: 
bluifh, in the form of fix-fided divergent prifms. Found 
in a valley near Tatarefchol in Tranlylvania, imbedded in 
yellow jafper. 
15. Chalcedonius viridis, or green chalcedony : green, 
femitranfparent, of a flatter texture. Found, though 
rarely, in the Feroe Ifland. Colour generally grafs-green, 
though fometimes approaching to the seruginous. 
16. Chalcedonius chryfoprafus, or chryfoprafe : green, 
with hardly any internal luftre, femitranfparent, of a flat¬ 
ter texture. Found in Germany, particularly near Bref¬ 
law in Silefia; generally in folid mafies, fometimes in 
loofe pebbles, or layers of albeftus, talc, lithomarg, and 
iron-ochre. Internally it is dull; it is hard, but does 
not ftrike fire with fteel. Colour various Ihades of green. 
In a heat of 130 0 of Wedgewood, it whitens and becomes 
opake, but does not melt before the blowpipe. Poliflied 
fpecimens of this fubftance are particularly beautiful on 
account of their colour; and fometimes they have a con- 
fiderable degree of tranfparency ; but it is difficult to ob¬ 
tain them of a large fize without flaws or clouded fpecks. 
Chryfoprafe is faid to lofe much of its colour when kept 
in a warm and dry place. Specific gravity, 3-25. Con¬ 
tains filex 96-16, oxyd of nickel x, lime 0-83, alumine o - o8, 
oxyd of iron o'8. This is the analyfis of Klaproth, whofe 
recent death (Jan. 1, 1817.) the Icientific world will long 
have caufe to lament. 
17. Chalcedonius heliotropius, or blood-ftone : diapha¬ 
nous, of a conchoidal texture; green, with blood-red 
dots. Found in Afia, Perfia, Siberia, Iceland, Bohemia, 
and Franconia, in rocks of trap. From the beauty of its 
poliflied furface, it is much ufed for ornamental purpofes, 
of fnuft-boxes, knife-handles. Sec. 
Adamas, the Diamond. — Confining of filex and carbon ; 
flightly ponderous, extremely hard, lamellar, exhibiting 
a high peculiar luftre, breaking into intermediate frag¬ 
ments, parafitical, ffiining in the dark after being expofed 
to the rays of the fun, attrafting light bodies when rubbed 
or heated ; crackling and lofing its tranfparency in the fire, 
and at 14 or 15 0 of Wedgewood begins to burn, and at 
length entirely evaporates. 
There is but one fpecies, Adamas pretiojifjbnits, of which 
there are eight varieties. The bell are found in Borneo, 
the provinces of Golconda and Vilapour, and at the foot 
of the Orixa mountains in Bengal; the lei's brilliant kinds 
in the diftrift of Serra do Frio, by Brafil, in South America, 
generally in loofe fand or incloled in a loamy earth, rarely 
aggregate or attached to other foffils. Of all mineral fub- 
llances it pollefles by far the greatell degree of liardnefs, 
tranfparency, and luftre; fraclure ftraight, and perfectly fo¬ 
liated. It is either colourlefs, or red, greeniih, yellowilh, 
browniffi, black, or fteel blue, with fometimes fpecks and 
clouds. It is of all gems the moft precious ; and, from 
its entirely confirming like an inflammable fubftance, may 
probably be conlidered as a very pure fpecies of coal: it 
is therefore now very generally confidered as an inflam¬ 
mable body ; and with Inflammable Subftances it is ac¬ 
cordingly clafled in the recent fyftem of Profeflbr Kidd. 
The Grand Duke of Tufcany was the firft perfon who 
afeertained that the diamond might be diffipated by the 
joint a£lion of heat and air: his experiments were con¬ 
ducted at Florence, in the year 1694, by means of a burn- 
ing-giafs. The emperor Francis I. repeated the fame ex¬ 
periment on the diamond, making ufe of the heat of a 
furnace: thefe experiments were made at Vienna5 and 
here alfo the diamonds employed on the occalion were 
entirely diffipated by the aftion of the fire. But, before 
the experiments of either of thefe princes, fir Ifaac New¬ 
ton, having obferved that the refractive power of tranl- 
Vol. XV. No. 1057, 
A L O G Y. Earths. 4(>~» 
parent fubftances was~, in general, in proportion to their 
denlity, but that of fubftances of equal denlity thofe which 
were inflammable poflefled the refpeftive power in a higher 
degree than thofe which were not, concluded, from a com¬ 
panion of the denfity and refraCtive power of the dia¬ 
mond, that it contained an inflammable principle. For 
a detail of modern experiments on the combuftion of th® 
diamond, fee the article Chemistry, vol. iv>p. 387-393. 
Some of the natural cryftals of the diamond have con¬ 
vex furfaces, or even approach to a fpheroidal form : but 
this is the natural form of the cryftal, and not the efteCl 
of attrition. Diamonds indeed can but rarely acquire a 
rounded or pebble form ; becaufe, being harder than all 
other fubftances, they cannot be rounded except by-mn- 
tual attrition ; and they feldom are accumulated in fuffi- 
cient abundance for this. The unpoliffied diamond may 
be diftinguilhed from the varieties of fapphire, from the 
hyacinth, and from quartz, See. in acquiring the vitreous 
or positive eleftricity by friCtion; whereas thofe fubftances 
acquire the refinous or negative; from the fpinell, by its 
fuperior hardnefs. See Diamond, vol. v. p. 789. 
Order VI. ADAMANTINE EARTH. 
Adamantinus, Diamond Spar.—Confifting of corunda, 
or adamantine earth, the greater part alumine, a little 
filex and iron ; very hard, ponderous, lamellar with ftraight 
foliations interfefting each other in a three-fold manner, 
breaking into rhomboidal fragments : perfectly apyrous, 
and yielding a little to the file. This Order confifts of a 
Angle genus, and the Genus of a Angle fpecies. 
Adamantinus corundum, imperfect corundum, or ada¬ 
mantine lpar. Found in China, Bombay, France, and 
Spain, in granite: colour grey, with often various fhades 
of green, blue, and brown : luftre tranlparent, and when 
poliflied fliines like mother of pearl: is fometimes found 
maffive, but moft commonly in fix-fided prifms. It is 
ufed like diamond-powder, for cutting and poliftiing hard 
minerals. Specific gravity, 3-981. Contains corunda and 
alumine 84, filex 6-4, oxyd of iron 7-5. 
Corundum is an Indian term, the meaning of which 
we are not acquainted with. The Chinefe corundum 
contains a little more than one tenth of its weight of 
magnetic iron ore, mechanically difi'eminated through its 
fubftance in particles of various fizes; fometimes as large 
as a hazel-nut: their form is indeterminate. The Bengal 
corundum contains no magnetic iron: a few grains are 
occalionally found in adhering to its furface. The Chi¬ 
nefe corundum is of a deep brownifh-green colour; that 
of Bengal is of a light yellowifh colour; of Malabar, a 
reddifh brown; of the Carnatic, a greyiffi or greenifh 
white. The laft-mentioned variety is moft commonly met 
with in cabinets ; and generally in fragments that more 
or lefs approach to a cubic form. The above varieties of 
corundum are met with in granitic rocks, of which they 
form a diftinft component part, after the manner of fel¬ 
fpar ; and their general appearance is indeed not unlike 
that of felfpar. 
The very ingenious Mr. Rafpe has drawn a plaufible 
inference in favour of his opinion, that India was the pa¬ 
rent of gem-engraving, from a local circumftance. The 
art of engraving on fubftances which only the diamond 
can penetrate, and only the peninfula of India could fup- 
ply, he feems to think could have originated in no other 
country. Commerce, attendant upon the extending 
pomp and luxury of the eall, gradually tranfported thefe 
precious materials to the weft and to the north ; but the 
ipeculations of the Egyptians, according to Mr. Rafpe, 
would never have induced them to break diamonds, or 
ftamp them in mortars, for the purpole of trying experi¬ 
ments; luch Ipeculations are more rationally to be ex¬ 
pelled in the neighbourhood of the mines of Golconda, 
the native country of the diamond and other hard ftones, 
where their properties and beauties mull be aicertained 
before they could become objects of exportation. In a 
fubfequent part of his Effay,Tie l'peaks of Hindoo engrav¬ 
ings ; and particularly of a lion in emerald in Mr/wil- 
6 C _ kins’s 
