Earths, 
MINERALOGY. 
Earths. 
461 
their furfaee. In fome parts of Germany, and'Bohemia, 
common garnets are employed as a flux in the reduction 
of iron ore; a purpofe to which they are particularly 
adapted, as they themfelves contain a confiderable pro¬ 
portion of iron. It is a remarkable faCt, that in fome in- 
flances the moft-perfeCHy-tranfparent garnets affeCt the 
magnetic needle. The garnet, when of a dodecahedral 
form, may be diftinguilhed from the hyacinth of the fame 
form by the angle under which its faces mutually incline 
to each other, which is in every inftance 120 0 ; while in 
the hyacinth it is fometimes greater, and fometimes lefs. 
On the fame principle it may alfo be diftinguifhed from 
dodecahedral hornblende, and fome of the varieties of 
ftaurolite. It may be diftinguilhed from leucite, by its 
fulibility and greater fpecific gravity; from the ruby and 
fpinell by its inferiority in colour and hardnefs, and by 
its fufibility. 
There is a curious paffage in Pliny, by which it appears 
that in his time imitations of the precious ftones were 
commonly made in glal’s, with foil, or fomething analo¬ 
gous to it, placed under it; but that they might be de¬ 
tected by their want of hardnefs, and inferior fpecific gra¬ 
vity. He makes the obfervation in fpeaking of the diffi¬ 
culty of diftinguilhing real from artificial carbuncles, or 
garnets: " Nec eft aliud difficilius quam difcernere base 
genera: tanta eft in eis occafio artis, fubditis per quae 
tranflucere cogantur: adulterantur vitro, fimillime; fed 
cote deprehenduntur, ficut alias gemmae faCtitias, mollior 
enimnatura: deprehenduntur et pondere, quod minus eft 
viircis." Nat. Hift. lib. xxxvii. For the practices of the 
moderns in this way, fee the articles Gem and Glass, 
vol. viii. 
17. Gemma granadillus, or red Ihorl: hard, rather pon¬ 
derous, red, of a parallelly-fibrous texture, melting with 
difficulty, in acicular prifmatic cryftals. Found in Swif- 
ferland, the Pyrenees, Caftile, Hungary, and Siberia; 
generally in quartz or granite. Colour from that of a 
peach-bloflom to a blood-red: diaphanous, Ihining Out¬ 
wardly, breaking into acute fragments, exhibiting con¬ 
vex faces when broken tranfverfely, and acquiring a high 
glofly polilh. Specific gravity, 3-1. Contains, in aoo parts, 
filex 114, alumine 70, magnefia 1, oxydes of iron and 
manganefe 10. 
Glucina, Glucine or Glycine.—We place this newly- 
difcovered earth here, becaufe it Was firft found in the 
beryl, and has been met with only in the beryl, the 
emerald, and another mineral lately found in Peru. The 
falts which it forms with acids are highly faccharine; 
hence the name. See the article Chemistry, vol. iv. 
p. 221. 
The generic characters of glucine, which are united in 
none of the other known earths, are: 1. Its falts are fac¬ 
charine, and (lightly aftringent; 2. It is very foluble in 
the fulphurie acid by excefs; 3. It decomposes the alumi¬ 
nous falts; 4. It is foluble in the carbonat of ammoniac; 
5-_ Is completely precipitated from its lolutions by ammo¬ 
niac ; '6. Its affinity for the acids is intermediate between 
magnefia and alumine; and its parts are not agglutinated - 
by heat, as thofe of alumine are. Specific gravity, 2-976. 
Glucine, _in its pure ftate, has not yet been difcovered 
in nature: indeed, its occurrence in compound minerals 
is exceedingly rare ; for it has only been found in the 
beryl, or ultramarine, the emerald, and the gadolinite; 
unci it enters but fparingly into the compofition of thefe 
bodies; the beryl, in which it is moft abundant, contain¬ 
ing, according to the analyfis of Vauquelin and Rofe, no 
more tlvan 14 per cent. From the analogy which exifts 
between glucine and alumine, the former is very liable to 
be taken for the latter by chemifts who do not pay parti¬ 
cular attention to accuracy in their analytical inquiries. 
The firft analyfes of the emerald made by Klaproth and 
Vauquelin afford an inftance of this kind : and M. Bind- 
ham committed a fimilar error in his analyfis of the beryl. 
_ Yttriaand alumine are the only earths for which glu¬ 
cine is liable to be miftaken; the properties in which it 
Vol. XV. No. 1057. 
refembles them are, rather unfortunately, of a moft ftrik- 
ing kind ; but it has a number of other characters which 
are very diftinCt, and fully demonftrative of its peculiar 
nature. Glucine is fimilar to alumine, in being foluble 
in cauftic folutions of the fixed alkalies, and in fome of 
its phyfical qualities; but it differs from alumine in af¬ 
fording with acids fweet aftringent falts ; in not yielding 
alum with fulphurie acid and potafli; in poffeffing a °reater 
affinity for acids; in being entirely foluble in’carbonat 
of ammonia; and laftly, in not being precipitated from 
its folutions by oxalat, tartrat, or pruffiat, of potafli. It 
is to be diftinguifhed from yttria, by its greater folubility 
in carbonat of ammonia, the latter requiring for its folu- 
tion five times as much carbonated alkali as glucine, bv 
its falts occafioning a precipitate when added to any of 
the fuccinats, by the infolubility of yttria in fixed alka¬ 
line folutions,. and by the precipitates which the falts of 
yttria afford with pruffiat of potafli. 
Glucine was confidered as a Ample body till the im¬ 
portant difeoveries of Dr. Davy gave rife to new analo¬ 
gies ; and, though the compound nature of this earth is 
not yet fully demonftrated, yet there is every reafon to 
believe that glucine, like the alkalies and alkaline earths 
is a metallic oxyd: and the refults of the experiments 
which Dr. Davy made on this body are explained beft on 
fuch a fuppofition. This gentleman negatively eleCtri- 
fied glucine, (lightly moiftened in con tad with an amal¬ 
gam of potaffium, under naphtha, by a battery of 500 
plates. After an hour, the amalgam was thrown into 
water, and an alkaline folution was produced, which 
became cloudy when neutralized by acid, thus indicating 
the prefence of the earth. Dr. Davy following the no¬ 
menclature which he has adopted in refpeCt to the ne\V 
metals,_ has propofed Glucium for the name of the met-al 
of glucine, when its exiftence is no longer doubtful. 
In no form, as yet, has this mineral been ufefully em¬ 
ployed ; yet Vauquelin conceives that the earth itfielf and 
fome of its falts, when they can be procured with facility, 
may admit of fuch an application in chemifty, in medi¬ 
cine, and the arts. Its marked attraction for animal and 
vegetable colounng-lubftances induced him to think that 
there was a probability of its being ferviceable as a mor¬ 
dant ; and the peculiar tafte of fome of its falts gave rife 
to the hope that thefe combinations might produce falu-- 
tary effects on the animal fyftem. If his expectations 
fliould be realized, we mult agree with Vauquelin, that 
thefe falts will be fome of the moft agreeable medicines 
that exift. Ann. de Chem. vol. xxvi. 155, xlu. 277. Aihin's 
Chan. Diet. vol. ii. Phil. Trmf. 180S. 
Yttria, Gadolinite.—-This earth alfo has been difed- 
vered iince Dr. Gmelin made his Claffiftca-tion. Profeffor 
Gadoliti, of Sweden, firft noticed this mineral, in the 
year 1794, at Ytterby in that kingdom.- hence the names. 
Generic characters: Confiding chiefly of yttria, filex 
oxyd of iron : it is found mafiive; ihining, vitreous; 
fraCture conehoidal. Colour velvet black-; Or browniffi 
black; opaque; hard; fief at dies quarts; brittle. Spe¬ 
cific gravity, 4-04. When reduced to pbwder, and heated 
in diluted nitric acid, it is converted into a thick yel- 
lowifh-grey jelly. Before the blowpipe it decrepitates" and 
becomes whitifh red, but remains infufib'le. It was firft 
analyzed by Mr. Eckeberg. The following are the con- 
ftituent parts according to him and others: 
Yttria - - - 
Silex - 
Lime - 
Alumine 
Oxyd of iron 
■---manganefe 
Water and carbonic acid 
Lofs - 
Eckeberg. 
Vauquelin. 
Klaproth. 
4 - 7'5 
35 ' 
5975 
25 ’ 
2 5'5 
21*25 
--- 
2* 
-- - 
- 4'5 
— 
S 
iS- 
2 5 ‘ 
1 7 ‘ S 
--- 
z * 
■ -- 
-— 
J 0'5 
•5 
S' 
- - 
‘5 
100*0 
100*0 
100*00 
6 B 
As 
