The name heliotrope was conferred upon this variety of quartz,
from the idea that when plunged in water it presents a red
reflection of the sun's image. There is a tradition, believed
in the age of superstition, that at the Crucifixion the blood of
Christ, falling upon a dark green jasper, produced the red spots.
This stone was used as a talisman by the Gnostics and later'
Egyptians, and was in great demand in the Byzantine and
Renaissance periods. The interesting myth that the heliotrope
was invested with certain magical properties by incantation,
when the person wearing it is made invisible, was boldly repudiated by Pliny, the practical old Roman, who had something
of the iconoclastic tendencies of modern scientists.
Some Egyptian and Babylonian intagli are found oa this
variety, but engravings of this kind are rare, though they occur
frequently with the Gnostics on green jasper mottled with
brown.
Cairngorm, a name given to smoky quartz, is derived from
a place in Scotland bearing the same title. Some authors
designate the variety of intense color " morion," and the transparent brown or yellow crystals "cairngorm," but among
lapidaries the cairngorm includes all shades of color, from
black to yellow, known by different appellations, as Brazilian
topaz, Mexican topaz, Spanish topaz, diamond of Alençon,
smoke-stone, etc. It has been by some antiquaries identified
with the mormorimi of Pliny, who calls it a transparent stone
of a deep black color,— a description better suited to the black
tourmaline, as far as color is concerned, than to the cairngorm.
This is a favorite gem with the Scotch jewellers, who cut it so
as to display its color and brilliancy in a remarkable degree.
Aventurine. — This is an epithet applied to varieties of
different species, having a peculiar construction, as well as to
an artificial production, first made in Venice, by a mixture of
