i j 8 N A T D 'R A L JH>1 S Î ' O R Y
as pure cryttals and as 'fpâr approaches hear, to cfyftal,'To does
cryftal oftentimes to the diàmond, in hardnefs^i^ftre, and refitting
o f fire. The ’ diamondris the‘*bafis of &11 >|ems, which ’iïT lïard-
nefs and; lettre ^ççeed .thejftate o f qryftal j . the. diamond-4s ^ eiçfcfe
but another remove, and in a more ferpihènt degree the Jape ftonc
and cement in' the utmoft perfection, v( and therefore rap) .which in
inferiour- ftates -of-purity wo call cï^ftàl arid -ipar. T o fcoTLe“o f tj|efe
three cements-all •ttones- ^hetherttrnple or'aggregate, ''m%y*be~faid
to owe their connexion anddblidity
than earth concreted • by ‘the intervention *df xemeiit, To as' to acquire
ha-rdnefs and weight fiiffiéient to denominate it à ftoncc.
If-thettone will ferment-with acid$:, Jfpon dfflSlve, 'be eâfily pîil-
verized, gives no fire with fteel, and'fhews other eViderït tymptbms
of Ipecifical ’fcftnels, it fe'then either Wholjy Ipar, or dr ajfpaflihfis';
on^the other-hand, if4t<réfitts acids, remains mdSsrâtely'firm under
the hammer; and in ^-ttrong fire) mixed wtth mt'anfle Jalt, win
turnantogîais, -upon edffifiqri with fleebgiyes'hre, and tfiTSS^nds
o f the engraver fhews evident figns of a 'fup'eritsuf jfafuneis, then
it is either cryftal or of a çiyftdline bàfis11.
Gryttal is die fofteft o f all peripicuous gems, whatever exceeds
it therefore in hardnefs is a gem, and if by a ftill greater degree of
purity than what is above-mentioned, the ttone becomes specifically
heavier, and of better luflxe than any other "meer ftonÿ Bodies, 'and
refills fire almoft to immutability, then if is 'called a aiamonla) and
all gems, the ruby* lapphir, and tüêrîteft," are but this diamond,:
iubftance tinged and reduced, a^TO'hjftre and
metalline admixture.
sect. ii. In Cornwall all the white, opake, common, hard lroriè?' is called
Offpv. Spar; errorjeoufly it mutt bç owned, for it is quaTfz, arid
not Ipar : but the Cornifh are not fingular in this poi'nf ; for i f any
thing could countenance erreur, ” they have the authority of the
greateft lithologifts in England (Mr. Eftuycf only excepted) of their
fide ■ . Indeed it mutt be acknowledged, that, till* witnfe tnele few
years, die diftinguifliing characters of thefe two Bodies- nave Hof-
been tttfficiently noticed in Eriglànd'; the lkte learned and ingenious
Dr. Ilaac Lawlon was among the fbremoft o f bUr countfymdn
who infilled upon their Being treated" always .as really dittinCt and*
‘-See-pageSo, note j | |
d If it is not nat^ralfy figured .and traofparent,
the.Get#13^ propedy .enough call lit. Quartz * that’
is, a coarfe, debafed, opake, crystalline body, and
jg&t cryftal, See page 91,
c> Iff is jiiftly 'obje£fced t6 Dfv Vv oodwird, thrft
hephanconfounded -fpat •and'cryftd) hf<all '•’hlsKtria-f ‘
tifes, without noting the obvious differences above-
mentioned'} and we- may fdy the1‘ fattife‘ 'of offtefs’,'
particularly of rhe learned Dr. Grew ( fee his
Muf. R. S. Part III Chap/ y.) though he had .
hi? acid menjiruum alwayrhefowr hirii.
different