too ' N A T ' U R A L H l ’S y Û ' R Y
the £ro»Wflovercoloured tranfparent qifartz, the grainfrom one-fixth
of an inch'diameter downwards these'is à giyra-lline, farinaceous,
fmall fanfl, inclofefl betwixt the grains, with a ^ f t 'quantity'of fil-
v!i^'tÛc^iàÉei^ôt^^--'|S6Æé diftancp oFtwodricHes,'generally more,
is a foot of black- cockle, half inch or under in diameter ; when the
foots are larger, they are1 more diftanri * If is dqmmonly called the
Silver Stone .;* arid indeed is of great lriftre in the microfcope, every
other granite placed by its: fide looking flat and -tame. It' is much
coveted for Walling in adder-work, being torigh; keeping a good
edge, and working eafy. One fpecimen weighed to water as
2 _ _ i î to i ; the fécond, of a more 'yellow ground, weighed more,
v iz. as 2 — to i . It imbibes water ftrongly, makes fip effer-
véfcence with acids, gives fire with fteel ; being calcined, |he black
fpots go olf, éven in a fmall firè; the talc will perpetually keep its
colour, though the other parts grow brown with age ; perhaps it
might do very well for filvering grounds for paper-hangings, and all
the ulès ó f talc.
Yellow gra- O f yellow granite there is a great quantity the ' g r o ^ f ^ & t h w h -
yellow, fpeckled throughout with black foliacéous talc of the fourth
o f an 'inch diameter arid under; the charge‘dark,- cloudy,'many
grains o f cockle from the fourth of an ’inch arid'uiickf in diameter,'
intermixed with large, toothy, whitifh, opake prifms of ..quartz,
from an inch and half long by an inch wide and' brider., ! The
ground of this ftorié being fb porous, and the chargés to frequent,'large
and hard, make it one o f the moft fhattery granites Vèykay^’ fit
only for rough works, where neither fquares, fharp edges^, nor
moldings are required. It weighs to water as 2 r - to 1 : it imbibes
water ftrongly, and difcharges it as - fudderily ; fb that walls
o f it muft be very damp.
Much better is the yellow granite of Tregóriin.' Its ground is
yellow, and being fomewhat earthy, riot more firm than the former ;
but then the grains of its\ charge are but from the fixth of an inch'
diameter downwards, and its black foecks of talc from the eighth
of an inch diameter and under, feeded fb thick, as to be ’ feldom
more than the eighth of an inch diflan t. This is a very beautiful
ftone, works as well as the white Tregonin before-mentioned, and
is therefore reckoned among our beft granites ; although I muft
obferve, that the ground is fo very earthy and tender in both, that
it can never bear a high polifh. It weighs to water nearly as the
white of this place, viz. as 2 - - ,z| to 1 : imbibes moifture ftrongly,
but evaporates it flowly, and is therefore much dryer for walling
than the foregoing.
Red granite. On the lands of Treaflo, in the parifh of Ludgvan, there is a
granite of a red ground, quartz laminated with oblong, lucid,
rhomboidal
O F C O R N W A L L . IOI
rhoriaboidal-fpak^, ffom the foyr{h of an inch diameter and ynder. '
TZUiftfurgo G°nfifts ’ ^{jlgltffky ejpereous granules, in, fome places
darkiand .fookle, nqfjaqly granuktej butjveined; .flie
, ground atj,d*t|^^|3|e'quall,y- harcfflp^hjs ftone at Treaflb is exactly
in ftry^yre^ancl -colou||^’the red Egyptian granite, and
ife jin . a,vein about# bo-y frofn&the jhqu&, • crofting the publipk
road 3f&hich lead-Srftol/Saftelatadinas^t^td may prove better at depth
than-at the top, f where I found it:^,It, weighs to watey,as ,2r- - I f lj
#,tQ. one.
-Of a richer, kind is the $ed granite firft taken nqtice -by, the'
difcerning Righ^ Honourable LordfEjfgcumbe, by whole direSons
Stables tyere firftlmade of^it,'. and vO|^h,apdfpme ftands forlb-ufts and
f 4fes. In th| new hajj,hA| MpunifEigg^mj^ hayeijbpen lately
{erected two chimjigy-^pieces prmcipally c^M s k in d , o f ftone; ^and
indeed to this noble Lord this beft^ojf our Cornifh granites' remark-
i able for; its bold - ruddy colouring sjnd high, and^^urable polidr^Tis
,£hfefly indebted for being refeued^fiom pbfeurity, and eftipnated at
To high a price as it is'at prefent hy.tfffi'curipi^. 5
fo foe,panfh .bf jEridgyan .there is?av granite, of’ a, .bjatk cocjde Black granite
ground^ charged fb thick with white fpots o f femitranfparcnt quartz,
from an irich^long by half inch wide’ and^under ;■ that the charge | ,
almoft 'rivals the ground in quantity,' it is much harder than cthe '
^ovp-coloured.* granite .’of thei feme parifh, and weighs to water, as'
■ 2 to - one. ,
Abetter ftonpiof the black kind is found ;;at Bofworlas, in ( th«e
-parifh of St. Juft;. the ground jjsipf a blacker cockle than the fore-
igrifogj and is interfiled" in all directions by toothy mafles o f a warm
Jlefh-colpured quartz, moftly in die parallelopiped fhape; fomey*
•times curvpd, now and then in a zig-zag manner, andrfometimes in
the' fbrm.ipf ri crofs; in diameter, ffom half to one-fixth o f an inch,
by two inchps long and under. The charge in depth confifts o f two
•Jivata (fometitnes three) of laminee) ffom the twentieth of an inch
ilthick and undel||yyitli^ lttcid furfaces parallel to one another, hut
dying at different-angles with thofe of the. adjoining firatum\\fo
that when one is oppofed to the light and fhines, the other, which
abutts at the end of it, does not. This is a moft .curious and beautiful
ftone, extremely hard; may be had in large pieces, and will
doubtfefs with labour attain, to a high polifh for tables, and ornaments.
It weighs to water as 2 - to 1.
The marble we have in Cormyall is not remarkable either for its se c t . viri.
beauty or pfe. In the parifh of Carantoc, and at New Kaye, in
Lower St. Columb, there is a coarfe cinereous marble veined with
white fpar: it ferments ftrongly with aqua forth) gives no fire with
D d fteel,