specific
gravity ranges from 3 to 3.25. Besides the transparent crystallized
forms, it is found in fibrous and granular masses. It is a common
mineral, and widely distributed. Its most common occurrence is in veins
accompanying ores of lead, silver, etc. It also forms beds. The
localities affording the best known, and in many respects the finest,
fluorite are Cumberland and Derbyshire, England. In these localities
the fluorite is known by the name of Blue John, or Derbyshire spar, and
is worked to some extent into large ornamental objects, such as
table-tops, vases, etc. These articles are turned on lathes, the stone
being first soaked in gum-water, or similar adhesive, to prevent its
falling apart. One of the finest pieces of this sort of work ever
executed is to be seen in the Museum of Practical Geology, London. This
object is a vase 2 feet 8 inches high, and 3 feet 7 inches in its
greatest circumference. It was made by Mr. Vallance, of Matlock, from
several pieces of fluorite occurring near Castleton, in Derbyshire.
The
mining district of Saxony affords large quantities of fluorite. Red is
one of the rarest colors exhibited by this mineral, and red fluorite
comes almost exclusively from the St. Gothard, Switzerland.
In
our own country many deposits of fluorite occur, though little use is
made of them for ornamental purposes. Macomb, New York, has furnished a
large quantity of green crystals, exceeding in size and equaling in
color any ever found. An extensive deposit of fluorite in Illinois is
mined for use as a flux, but the crystals are rarely clear enough for
ornamental use.
