The mineral world contains many beautiful materials that are without the pale which encloses the clearly defined gem stones; these "outlanders" may be classed as semi-precious stones that are only occasionally used, and while many are truly beautiful and others are interesting, because of rarity or peculiarities, all lack some quality--usually a sufficient degree of hardness--which would admit them into the patrician rank of Precious Stones. Because of their intense scientific interest, technical mineralogists, who have written books about gems, not only include but devote considerable space to minerals that will not meet the eye of one manufacturing jeweller or gem dealer in one hundred, or ever be seen by one gem buyer in thousands. These stones are usually not so rare in nature as they are in stores, and their cutting and mounting is usually the result of an individual order; otherwise they are collected and cut only for collector's specimens. Brief mention will be here given to some of the minerals that occasionally appear and are included in the stocks of the principal stone merchants. In the American market there is a difference in this respect between the market east of the Pacific coast cities and localities near them or close to the Rocky Mountains and the Sierras, because that mountainous region is a great mineral treasure house, yielding many welcome finds of attractive and beautiful semi-precious stones; therefore in San Francisco, Denver, and other Western cities, these local minerals are used in jewelry to a greater extent than they are in the midland cities and those of the Eastern States.
Among the stones most likely to appear from time to time in the shops are:
LABRADORITE, sometimes, in the trade, called labrador, is a feldspar. Because of its structure some of the varieties of labradorite reveal a wonderful variety of colours. Labradorite can be highly polished and exhibits beautiful chatoyant reflections.
LAPIS-LAZULI was long regarded as a separate specific mineral; it was the sapphire of the Greeks, Romans, and the Hebrew Scriptures. Instead of being a simple mineral, lapis-lazuli consists of a bluish substance (lazurite) with granular calcite, scapolite, diopside, amphibole mica, pyrite, etc. The hardness of lapis-lazuli is 5.5; specific gravity, about 2 to 4; lustre, vitreous; translucent to opaque.
LAVA can hardly be classed as a semi-precious stone, but it is and has been quite extensively utilised in jewelry, chiefly on account of sentimental association with, and as souvenirs of, volcanoes. Lava is the fusion of various mineral substances due to the heat and force of eruptions from the interior of the earth; it varies in structure and constituents, but the surface lava is usually massive with vesicular or porous marks; fracture, splintery and conchoidal; lustre, dull or glistening; it is opaque and of various colours and shades. Lava frequently contains crystals--feldspar, lenate, hornblende, garnet, and other minerals. Vesuvian lava of a blue tint resembles transparent enamel, and is mounted in brooches and rings; cameos and intaglios are sometimes cut on it.
MAGNETITE, or lodestone, possessing polarity, is used for charms, because of the mystical properties attributed to it.
MALACHITE is carbonate of copper of a bright green colour. When this copper ore occurs in conjunction with azurite, the companion minerals are cut together, with a pleasing effect.
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Precious Stones Guide Vol 4
>> About SemiPrecious Stones: Labradorite, Lapus Lazuli, Lava, Magnetite, and Malachite
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