This
common and widely distributed mineral occasionally affords transparent
crystals which admit of limited use in jewelry. The cut stones cannot,
however, endure much wear, as the hardness of the mineral is only 5.
The colors which the crystals may present are violet, light blue,
yellow, rose, and various shades of green. One color and degree of
transparency may characterize an entire crystal, or but a portion of
one. The crystals have nearly always the shape of a simple hexagonal
prism, the mineral crystallizing in the hexagonal system. In
composition apatite is phosphate of lime, with a small percentage of
fluorine or chlorine. It is, therefore, much like bone in
constitution. It is barely fusible before the blowpipe. On moistening
a fragment with sulphuric acid, and heating, the flame is colored pale
green from the phosphorus present. Apatite is attacked and dissolved by
strong acids. Its specific gravity is 3.17-3.23. Its luster is vitreous
to subresinous.
The
best known transparent apatite is obtained at Ehrenfriedersdorf, in
Saxony. Here transparent crystals of a violet color occur capable of
affording cut stones of a few carats in weight. From Arendal, Norway,
greenish-blue crystals are obtained, furnishing the variety known as
moroxite. A yellowish - green variety, known as asparagus stone, comes
from Murcia, Spain. At Mount Apatite, Auburn, Maine, crystals of pink,
green, and violet colors have been obtained which sufficiently
resembled tourmaline to be mistaken for it.
Apatite
occurs most commonly in metamorphic crystalline rocks, especially
limestone. It is also found in granites and mica schists, and in
sedimentary rocks; but in the latter it is usually an amorphous mineral.
