GEMS. 
{pots confiderably leffen the value of oe and that 
perfons concerned in their fale endeavour to fre ee t nem from 
ee ‘This procefs, how 
fired effeét ; ce fometines ae Gan will encreate in fize, 
colour for one perhaps ftill lefs deli rable, 
e the. blow-pipe in bor 
ie difiufed red, like ‘hat of ie ik as ruby, and it was 
fold with great profit asa red diamond. Another, however, 
with a {peck a sparently of he bie kind, when expofed to 
the flame of the blo ow-pipe, yoga aap throughout, by 
- which change of colour its value of courfe confiderably 
diminifhed. to the choice of oie) diamonds, (we 
tranfcribe what Mr. Allen. has faid on this fubje@t in a paper 
inferted in the Philofophical Magazine, ) great care fhould be 
taken in regard to their colour, their bei ae ree from extra- 
matter, and their perfect are 
otptae water, in 
the middle of which you _ perceive a a feong hight playing 
iri if the t be fmooth and 
with green, then beware of it ; itis a foft greafy ftone, and 
will prove bad. 
fa ftone hasa rough coat that you can hardly fee through 
it, and the coat be white, and look as if it was rough by art, 
ae clear of flaws or veins, and no cnet caft in the body 
the ftone, which may be difcovered by holding it againit 
de light, the {tone will prove goo 
t often happens that a ftone {hall : appear of a sare hue 
on the outward coat, not unlike the colour of rufty iron, 
yet, by lookin 8 eee it againft the light, you ny obferve 
the = of the ftone to be white ; and dif there be any black 
{pots, or flaws or veins in it, which by a true eye may be 
dieorsre, although, ie coat of the {tone be opaque, fuch 
fton nerally 
re a réeiiifls bright coat, refembling 
a piece of green oe ila to black, it generally proves 
hard and feldom bad; fuch fLones have been known to be of 
the firit water, but f any tin€iure of yellow feems to run 
within it you may depend upon its being a bad fton 
{tones of a milky coat, whether the coat be bright or 
dull, if ever fo little inclining to - blueifh caft, are natu- 
wed in the cutting ; and 
mon-colou an coat a 
mixed with a little ee then they a are idea bad, and 
are accounted amongit the worft of colo 
The greateft care muft be taken to avoi ia beamy ftones ; 
and this requires greater fill and practice than case jewellers 
are equal to. veamy ftones are meant fuch as look fair 
el 
or labour can polifh them; they 
of fometimes through all: when they 
ees on the utice, they fhow themfelves ike ea 
‘name might have been conveniently ex 
excrefcences, from whence run innumerable imall pe 
as eae ae each othe 
e ston h i 
ining, 
eae and fibre es fhoot Sia and the 
in the coat of the diamond. Stones having thefe properties 
are difficultly cut, and will never take a P 
ne fyftematic writers have given ie name of wa di 
he. 
mond to the {pinel-ruby, probably on account of fimilarity 
in their cryftallization. The {mall cryftallized fparkling 
mian, » Hungarian, . nae Canadian, Afturian 
Miioues. “diamond of Bafla, of Alengon, Dauphiny, &c. 
Supphire—The gem next in hardnefs to the ae mond. is 
the fapphire, ge oie g, as wartelien -all thofe precious ftones | 
that are know na z 
oriental ruby, the oriental topaze, the o 
All thefe, eles together, form a fab “Aivifion of that affem- 
blage of hard ftones denominated corundum ; Ww which 
chang’ 
ter adapted to European ears. The 
the adamantine fpar corundum with the fap hires, ° 
firft oceurred to Romé del’Ifle, and his idea was afterwards 
followed up, with much acutenefs of obfervation, by count 
-Bournon, who divides the corundum, according to the two 
different ftates in which it exhibits itfelf, into perfed and im- 
n 
‘telefie, that mineralogift now ditinguither [ his owe (a the 
name ba corindon hyalin. 
neral the name of fapphire is given to the blue — - 
eo is either of a deep indigo blue, (now and then called 
the male Japphire by lapidaries,) or of various lighter ae 
feveral of which are fometimes to be feen in one and the 
cryftal: the paleft are femetimes called female, or 
ame 
‘water fapphires, w ek latter denomination is alfo applied to 
a blue variety of quartz. The fapphire, more frequently 
than the red variety, or ruby, gradually paffes into perfectly 
white or colourlefs, which, when cut, may almoft pafs fora 
d 
iamon 
&< 
A good fapphire of ten carats is valued at 50 Sie 
f it weigh twenty —- its value guineas ; 
but under ten carats, may be valued by motiplying 
the carat at 10 fhillings a Capen into the fquare of i 
weight. 
The red variety of fapphire.is called oriatal ruby. 
id cochineal and chr 
which, without confulting other cha araciers, is imme diately 
known from amethytt shay by its fuperior luftre. cad 
perfect ruby, abov e 33 carats, is more valuable*than a 
diamond of the fame weight. If it weighs one. carat it is 
worth 10 guincas; two carats, 40 guineas; three carats, 
150 guineas ; fix carats, above 1000 guine A. deep co- 
loured ruby, excceding twenty carats "ight, is generally. | 
re carbuncle. f n the thro 
the great mogul, 1©O to 200 carats 
” Sa apphire alivoccurs a pee colour, and is aioe fuc 
by the name of the oricntal topaze. Its tint is generally es 
tween the dark yellow os a br ala, ae ie e pale ycllow o 
the Saxon topaze. An i blue to this colour 
. produces 
