S E C T . II.
Shapes.
When ironfformilby dropping fromroofs; abd - fidb -of'cavesy it
becomes a lump of tubular parallel ftems which hang fide b f fide
in the fame manner as the mundics,. Plate xv.i. page 1 4 ^ Figures
xxxiv, xxxv. and copper, Plate xxi. Fig. ix. and is called Brufli-
oie. Sometimes it is found in the forin and fize of^muflcet bnllet-s ,
Plate xx. Fig. XXXI. page 1S6,. each of which is:fixed in its nidify
but. never detached and perfectly globular, as far as I ha^e yét feéni
Dr. Grew (Muf. R. S. page 332) mentions iron balls made by the
rolling of iron-fand off the banks among the iron-inines öéar Sen-
neck, efpecially after rain ; but thefe here are natural from thé
mine. Sometimes it is bliftcred into round tubercles, as Plate xv.
Fig. ix. page 137, and Plate xxi. Fig. h i . at other times madé
into the exa& fhape of a button, protuberant in the middle, arid
declining on every fide into1 a variety of polygonal planes, as Fig.-
XXXII. Plate xx. In both thefe laft cafes it is called the Button-ore.
Iron is faid to give the rhomboidal form to cryftàls ° : if this be true,
it may alfo do the fame to mundics ; but, as the rhomboidal form
is not peculiar to iron, the queftion wifi ftill ■ remain undecidei^
whether one and the feme mineral felt may not give this figure to
them all, and be no more the proper confequence of iron than of
the other folfils. This ore is fometimes found in Cornwall, near
Truro, confifting o f parallel plates which break into very fhinidg
and gloffy furfaces w, and a coarfe falfe kind of iron-ore, called Kal,
is found in moft parts of Cornwall; this laft promotes’the fufion
and toughnefs of tin, efpecially where mundic abounds ; for the
mundic by itfelf will fcarce permit the tin in many places to. be at
all duétile : the truth is, the Kal confiées the metallic parts,
whereas the fulphurs of mundic have a quite Contrary effect, and
render them volatile,
C H A P. XV. ;
O f the Cofper found in Cornwall.
T H I S fupple, rich, and ufeful metal, Cornwall has for fame
ages been reckoned to have been plentifully flocked with*,
but it has never turned out any confiderable profit to the owners
of the land till within thefe fixity years'; fo little does difcbvery fig-
nify, unlefs it be purfued with application, and knowledge how to
make the proper advantage of it. At prefent it may be aflerted
* As in Huel-an-boys, in St; Juft, | f | Woodward’s Gat. vol. II. page 86.
0 Woodward’s Cat. vol, I. page 220. Hill, * See Carew's Survey, page 7 . Norden, pagff
page 197. ' . :v r . 9> "I04-
with
with great fecurity, that tliere is no richer copper, not ,a greater
variety o f ores any where than., in Cornwall.
Copper is found fometimes depofited on the fides o f fiflures. in sjjct. i.
thin films, which are no
from fame coppeitiiode ; fometinies in foots ;a$d bunches irregularly;
difoerfed, but moftly in fiffures, in like mainema# th© fin-lpefes. 3
Copper lodes throw from thenriffeW fhodes, fo that they are not
often acceflary to their own difeovery; the reafoni'pf whi^h is, that
there is feldom any copper on the back of the Ipde, fo'as tfi conftitute
a broil\ but when there is, and that copper is heavyi a^d promotes’ i t f
own removal downwards by its gravity, copper lodes throw (bodes as^ jj
Well as thofe o f iiin, o f which feveral inftances toight be produced.
- Veins o f copper are oftentimes by the fedqlous difeovff*ed in ‘cliffs,
where-they are laid) bare by the fea, copper being much maffersdif-
cerned than tin. T he moft encouraging leader to copper is what ’
the Comfth call Goffen, which is an earthy, ochrous frone, ruddy
and crumbling, like the ruft o f iron.; Where the ground is foeli-
nablc to an eafy, free,.bluS'killas, intermixed with. white clay, fthfi
miners think it a promifing fymptom. A white cryftalline ftone i$
alfo reckoned very retentive • o f yellow copper, T he pr<p does not
lye at any-One certain depth;- but it is a general rule, that when
copper is found in afiy lolled that ’lode fhoiild ‘be funk upon, *11?
generally proving better at fbme depth, than'when it i? frrft t
touched.
S „T h a t ore which ism oft common is o f a yellow bra^-eolour: it£s ect-. ii.
is found adhering to ftones o f all kinds, but pureft commonly
the white opake cryftal, or in the white clay, and according to jfre-ioursand- 4
quantity o f the barren ftone intermixed, fells from five to fifteen
pounds per ton. O f this yellow ore there are different forts : fonje
not only looks like mundic in texture, but is fhaped into cubes (as
the yellow munihe generally is) and will bear aqua forth without
frxrring, and yet has been, found, to be real copper-ore, and worth
eighteen pounds per tori; but the boft fort o f yellow is the jffake-
ore, called fo from the clofenefs o f its texture, which is .as finootfr
and glofly as brafs, and not more porous: this fort is not fo brittle
as the former yellow, and has undergone the purification s f ? a mp-*
Jlruum, being probably no more than the firft-meorioned common
yellow diffolved and depofited5in the mine: it is found commonly
in thin, -vifibly diftind, ftratous- maffes, with its under parts o f:
a Miftered buttony forfaee, (Plate xxi. Fig, mi) anoording as foe
drops o f the folution fell from different parts o f the roof | Plate fo.
Figi i i .). Where the folution is vifeous and Ws diluted, it forms tubular
E e' e ® * ’51 ‘ ‘ ' ' 1 * (heaths