ferric
oxide gives a bright red; the hydrated oxide of iron, Limonite, imparts
various shades of yellow. Some of the minerals allied to Chlorite and
Saponite impart a dark leek green ; more rarely a grey-blue is seen, or
black. It has a dull lustre and a large conchoidal fracture. The
impurities may amount to as much as 20 per cent, of the substance. What
has been said of the origin, application, and cutting of Agate applies
to Jasper in most cases, only two special kinds demanding further
notice.
Egyptian
Jasper is a form occurring in nodules in the Egyptian deserts and
showing the characteristic surface erosion caused by blown sand. The
nodules are derived from the nummulite roeks, and are of a general
brownish colour, showing concentric markings outlined in various shades
of brown and yellow.
Wood
Jasper is a fossil wood silicified. On polishing, all the structure of
the wood is well seen. It may occur with the silica in a colourless
form, when it would be more rightly classed with Chalcedony or Quartz.
It is not often used now for ornament, except perhaps for inlaying
work, but it was used in ancient times much more. It is found at
Chalcedony Park, Arizona, and Yellowstone Park, in North America.
The
localities where Jasper is found are numerous and widely distributed.
Many very beautiful varieties are found in Scotland, chiefly in
association with the Old Eed Pocks, as in the neighbourhood of
Edinburgh, in the Garleton Hills, and at Burn Anne, near Galston. Red
Jaspers are largely obtained from various parts of GerÂmany, yellow
from Sicily, green from the Urals, and blue from Bohemia.
