Gypfum or alabafter, is generally To foft
as to be fcraped with the nail; but fome
forts are much harder than others* and of
a clofer texture. Near the furface it is ftriated
and fometimes cryftallized; below it is much
more compad, and is frequently ufed for
architectural purpofes, forming elegant columns,
pilaftres, & c. of which thofe in the
hall of Lord Scarfdales, at Kedlefton, ftand
unrivalled. v When cryftallized it is called
felenite. It is eafily calcined, and then
forms what is called plaifter of Paris, which
greedily abforbs water, andjs caft into various
figures, as imitations of the antique fta-
tutes, &c. It is likewife ufed for moulds,
for floors in houfes and other economical
purpofes. It forms an article of trade, and
confiderable quantities are fent to London.
The chief varieties of this fubftance are
capillary gypfum, in delicate filky filaments,
three or four inches long, fo tender as to
render it impoflible to procure it perfed.
Plumofe
Plumofe gypfum, like white feathers,
elegantly curled, on limeftone.
Green felenite, extremely rare.
Selenite in tranfparent prifins and rhombs.
Gypfum, rock alabafter. Striated filky
alabafter.
Compad white; femi-tranfparent; red
Veined ; variegated, &c.
I {hall now give a fhort detail of the
other minerals and metals found in Derby-
fhire. '
In the filiceous order may firft be mentioned
topazine and rofe coloured quartz,
in hexagonal prifins, with double pyramids
detached.
Amethiftine quartz finely tinged; with
perfed hexagonal prifms, aifo with double
pyramids detached.
Clear - eolourlefs quartz in fragments, and
the fame enclofing bitumen : thefe varieties
are loofe in the limeftone.
/ G S Chert,