Jasper
Posted on June 17, 2008
Filed Under Uncategorized |
Jasper is a massive, compact quartz, usually containing many impurities. Opaque, dark red, brown, yellow, green, or gray, the included ferric oxides, iron silicates, and clay give rise to the different colors, which are all rather dull. The internal structure is so fine that the constituents cannot be recognized except by analysis.
Although used on occasions for larger decorative work, the material is uninteresting. A certain quantity is used normally to imitate lapis lazuli, but it first requires to be stained. Its porosity varies, so a uniform blue color is not always obtained. The resulting material is marketed under the well known name of Swiss Lapis. It has no connection with the genuine lapis lazuli, even the blue color seldom being analogous. Moreover, the color is fugi tive and quickly fades to that of the natural stone, which is generally an uninteresting gray. The specks of iron pyrites so often seen in lapis lazuli are always absent. It could be used for wedding ring.
The blue color is obtained by various processes, some of which are more successful than others. Berlin blue is used as a coloring agent, and other methods used are described in the chapter dealing with the staining of stones.
The natural stone is often named either according to its color or to its place of occurrence. Thus we have Egyptian, red, yellow, green, eye, and ribbon jaspers, while silex is a general name for jasper, which is now seldom used. The stone is very widely distributed, Canada (Ontario), U.S.A., Germany, the U.S.S.R., and Sicily being among the producers of usable material. It is found chiefly in mountainous districts; there is a hill near Chkalov in the U.S.S.R. which is entirely composed of pale green and deep red jaspers.
As an ornamental stone, jasper has been used for many centuries. Engraved rings of this material have been found in the buried cities of Pompeii and Herculaneum, as well as in many other ancient sites.
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