r V>'. 
[ 2 5 ° ] 
XIV. An Rnquiry into the original State and 
Properties of Spar, a?id Sparry Product ons, 
particularly , the Spars, or Cryftals found 
in the Cornifti Mines , called Cornifti Dia- 
monds. In a Letter to Emanuel Mendez da 
Cofta, Efq\ F, R.S. from the Rev. Mr. Wm. 
Borlace. 
Read Dec. 14, 1749. 
May 3, 1750. 
S'. 
SIR > 
N C E among your Searches 
into Natural Hirtory, you think 
it worth your while to be particularly inquifitive 
after our cryftallized Spars, commonly called Cornijh 
Diamonds '■> I will give you the beft Information I 
can concerning them, alluring myfelf, that you will 
make proper Allowances for the want of fuch Af- 
fiftances as are not to be had in my prefent Situa- 
tion. 
I {hall confide, r Spar here, as the Genus, at the Head 
not only of all the Species of common Spar, and In- 
cruftations of what Colour foever, but of Cryftals and 
Gems, which are here underftood only as finer and 
purer Subftances of the Spar Kind (1). 
' . . r > There 
(1) The Properries of Cryftal affigned by a late Trsacife {Mr. 
Hill’r Nat. Hiji. of FoJJlls ), fuch as keeping itfeif unaffected 
by Acid Menftrua, remaining unaltered in a moderate Fire, and 
giving forth Sparks of Fire by Collifion (whereby that Author dif- 
tmguifhes it from Spar), are here reckoned, rather to be accidental 
and claffical Differences, owing to a purer ftony Juice, lefs friable 
and 
s 
