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Variscite
resembles turquois in many properties, being, like that mineral, an
opaque, hydrous phosphate of aluminum not occurring in distinct
crystals. Its color is, however, normally an apple-green to
emerald-green rather than blue, and its luster is more nearly vitreous
than that of turquois. Its hardness is not equal to that of turquois,
being but 4. Its specific gravity is 2.4. It is infusible before the
blowpipe, but becomes white and colors the flame deep bluish-green on
heating. The only form of it that has been used to any extent for gem
purposes is one found in Cedar Valley, Tooele County, Utah. This is of
a bright green color, and occurs as nodules in a crystalline limestone.
Pieces of this give a pleasing effect when employed in jewelry in a
manner similar to turquois.
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CALLAINITE
This
mineral has been found only in a Celtic grove at Mani-er-H'rock, near
Lockmariaquer, in Brittany. It is there preserved in the form of
rounded pieces in size between a flaxseed and a pigeon's egg, and was
doubtless employed by the ancient Celts as an ornamental stone. Where
they obtained it has never been learned. It is a hydrous phosphate of
aluminum of a green color, spotted with whitish and bluish. Its
hardness is 3.5 to 4; specific gravity 2.5. It is opaque to
translucent. On account of its historic (or prehistoric) interest
pieces have been cut and used to some extent in jewelry; but its
employment can obviously not be extensive on account of the small
amount known. The name cal-lainite comes from callais, a
precious stone mentioned by Pliny, the exact nature of which is not
known, although it is generally supposed to have been turquois.
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