„ 6 N A T U R A L H T S T O R Y
N°. vii. What we call Gomifti diamonds are figured cryftals, and among,
cryftals we fiiall treat of them ; but feme efooi^,cryftals'are tinged
with green : they ayre of the Emerald kind ; what I have feen came
moftly from a copper-work in the parilh of Camborn, called the
Long-clofe v the Oriental emerald is a moft beautiful gem ;- for
the occidental, the jewellers1 ulually fell, this tinged cryfta],- common
cryftal being as hard as the occidental emerald ; with us it is1
angular or columnar, but beft when'found in, the pebble form, of
which I have yet met none in- Cornwall.
Nvyiii. Some of our cryftals are falfo.’of a fea-green or beryll
colour, and the fame which authors call the Pfeudoberyllus : after
burnt red-hot, they will retain their lhining in-the darkf for à few
minutes only, in this falling fliort of the fmaragdus which fhines à
confiderable time', but, Hke that, change their green into a pale % -
blue whilft hot, but recover ^their native-colour as they cool.
N°. ix. But of our curious green ftones, none'cdiïie’ near theèolôur and
poliih of a green cupreous incruftation found in Huel-fortune, in the
pariflx erf Ludgvan. Its texture is ftratous, cruft within' cruft ; its
furface puculated ; the tubercles which it forms'on the ftones, are
fnmptimw an inch in diameter, fometimes finall, and either perfectly
roimd or truly oval; the colour fo deep a green, and fo'high
a polilh, that I have obliged lèverai gentlemen-with feme to' fçt in
rings, for which nature has fitted them without the aid ôfr a-jeweller.
This comes very near to the properties of the' occidental
turcois, and has been taken for filch by Naturalifts. I hâve', from
the fstmet place, this copper o f a blueilh green clouded, but “tub*
green appears even there in fome parts,' and in the -greatèft ‘ part of
die fpecimens, the green is predominant and' urimixed. The blue-
turctois is generally efteemed a precious ftone, but indeed'no other
than foffil bone, or ivory faturated with copper diflblved in an alkaline
menftruum ; the green-turcois is the fame fubftance intimately
penetrated by a cupreous matter diflblved in an ■ âcid trtèn-
firuum, but this precious ftone from our Cornilh mines is the aerugo
or a plain fblution of copper, as appears by its forming itfelf into
threads and ftratous incruftationsz. I have met with none of this
kind o f any value but from this work, and it has been found there
only in one fmall cavity of about one foot and a half in diameter •.
1 HiD, 596. .
1 Dr. Grew’s Muf. R. S. page 287. ,
* “ The turcois i» much fofter than cryftal.”
Grew’s Muf. R. S. page 284.
« Fjg, xiv. and xv. Plate XXI. have their tubercles
of this beautiful green enamel,
C H A P .
o - C O R N W A L L. 117
H , P, . XI. \
Çfjthe'~gençrdl~èàfes~ofiÿtçhe^ vizi \bfSpa^%rÿftkt, "' 'M Dïàmond.
T H E R E iSjjjf’]fond of flany -lapidifici, matter whicji runs
^ through (iand ^nixes m o re |o r j^ } with the fubftance- of all
ftones, andj. may juftl^be efteemqd the univerfal cement, by^ which
earth and minerals'^combinedifeinto all,theffevtejal orders andfpe-
ciesfof ftones, fg r when this cements, t diffipated J^fi^ g o r diffolf
’Hfd’ hy a menftruum, the^ftme becornes, earth orapijet^J,; and ceafes
tp beVftond : » it i^ o f, itfelf itranlpa^^|v and* colcrurlels, ’, but when
mixed, is. found, either, oft that colour .which -.the- materials it joins
together were o§feefore they became ftone, or ,ofj , that .which?-any
after’^nfeCtion from other bodies, has imparted. |
^ This cement is either fpai^cryftai, or .diamond.’ ,<jThefe I fhall not
only treat o f as-.being.diftinCt ftones, in figure^mature, ,and effeCt, <but
as one', univerfal cement, running through ,and connecting all other
ftones in three.degrees.of,purity and perfection.. .Thus for inftance
iparriot only forms fimple.ftones ,o£ti;ts kind fiich a&ïheftapis fpecui
/^«y-double refracting and fimple refracting fpar, - ftalaCtites and the
like, buttis, indeed the bafis of a great number of compound ftopes,V
frbm the tendered lithophytes to;thqj^ardeft marbles» 'Soagain, cryftal
noLtiiily. forms hexagonal columns,* and cupides,. pyramids, and : the
like,: .but is the gluten;'the' connecting bafis of flat, folks, granite, flint,'
porphyry, -and the’Hke;' as diamond is-, allô the' bale The,
ftap*of ipar is the moft impure, its parts are calcarious, lax, difi-
perfed, they ferment and give w,ayto acids, are extracted, fuipended,
and wafhed aw;ay by common water, confequendy the ftonjes which
it combings are foft, brittle, : and eafily diflblved ; this ,is the cafe of
all. ftalaCtical productions, of alahafter, free-ftones, lime-ftones, and
moft forts of marbles, of which the cement is► fpar. But .the
Cement of ipar is not always equally weak, ibmetime^ it; will fcareé
ferment at all, gives-tiSre with fted 1-, and. it approaches fo near
the ftate of cryftal, in hardnefe^tranlparency, and figure, that it
is juftly called çryftalline fpar. ,
Î Cryftal has nothing calcaripus, in it, it’s parts .unite ,clofe and
firmly, and confequently formss much harder ftones than ipar, with
equal quantity of earth, fand, or whatever the charge .or, materials
in grofs may confift of;-’ and this-is the cafe ,'crf porphyry, granite,
jalper, and other compound ftonés, (whofe bafis is cryftal) as well
k See the Spatum compaffwn fcintillanp Linneel Syji. N a t. gen. vi..page 167.
H h as