ii8 NATURAL HISTORY 
as pure cryftals ; and as fpar approaches near to cryftal, fo does 
cryftal oftentimes to the diamond, in hardnefs, luftre, and refilling 
of fire. The diamond is the bails of all gems, which in hard- 
nefs and luftre exceed the ftate of cryftal ; the diamond is therefore 
but another remove, and in a more eminent degree the fame ftone 
and cement in the utmoft perfection, (and therefore rare) which in 
inferiour ftates of purity we call cryftal and fpar. To one of thefe 
three cements all ftones whether ftmple or aggregate, may be faid 
to owe their connexion and folidity ; a ftone being nothing more 
than earth concreted by the intervention of cement, fo as to acquire 
hardnefs and weight fufficient to denominate it a ftone c . 
If the ftone will ferment with acids, foon diflolve, be eaftly pul- 
verized, gives no fire with fteel, and fhews other evident fymptoms 
of fpecifical foftnefs, it is then either wholly fpar, or of a fpar bafis ; 
on the other hand, if it refills acids, remains moderately firm under 
the hammer, and in a ftrong fire, mixed with alcaline fait, will 
turn into glafs, upon collifion with fteel gives fire, and in the hands 
of the engraver Ihews evident figns of a fuperiour hardnefs, then 
it is either cryftal or of a cryftalline bafis d . 
Cryftal is the fofteft of all perfpicuous 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 ftone becomes fpecifically 
heavier, and of better luftre than any other meer ftony bodies, and 
refills fire almoft to immutability, then it is called a diamond, and 
all gems, the ruby, fapphir, and the reft, are but this diamond, 
fubftance tinged and reduced, as to luftre and hardnefs, by fome 
metalline admixture. 
sect. ii. In Cornwall all the white, opake, common, hard ftone, is called 
Of fpar. Spar ; erroneoufly it mull be owned, for it is quartz, and 
not fpar : but the Cornifh are not lingular in this point ; for if any 
thing could countenance errour, they have the authority of the 
greateft lithologifts in England (Mr. Lhuyd only excepted) of their 
fide '. Indeed it mull be acknowledged, that, till within thefe few 
years, the diftinguilhing characters of thefe two bodies have not 
been fufficiently noticed in England ; the late learned and ingeni- 
ous Dr. Ilaac Lawfon was among the foremoft of our countrymen 
who infilled upon their being treated always as really diftind and 
c See page 80, note b. 
d If it is not naturally figured and tranfparent, 
the Germans properly enough call it Quartz; that 
is, a coarfe, debafed, opake, cryftalline body, and 
not cryftal. See page 91. 
e It is juftly objected to Dr. Woodward, that 
he has confounded fpar and cryftal in all his trea- 
ties, without noting the obvious differences above- 
mentioned 5 and we may fay the fame of others, 
particularly of rhe learned Dr. Grew ( fee his 
Muf.’R. S. Part III- Chap, v.) though he had 
his acid menjiruum always before him. 
different 
