About SemiPrecious Stones: Diopside, Dioptase, Fluorite, Gold Quartz, Hematite, Iolite, and Jet

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:

DIOPSIDE is a variety of pyroxene; hardness, 5 to 6; lustre, vitreous or greasy; transparent to translucent; and doubly refractive. Fine specimens, fit for gem purposes, are found near DeKalb, St. Lawrence County, New York. When cut brilliant, diopside makes a very attractive stone and resembles green tourmaline.

DIOPTASE is a silicate of copper; other names for it are achirite and Congo emerald; hardness, 5. The softness and brittleness of this attractive stone disqualify it for extensive use.

FLUORITE or fluorspar, of which chlorophane or cobra stone is a variety, is a highly lustrous, brittle crystal of wide colour range; hardness, 4. Varieties of fluorspar are sometimes termed, in the trade, "false" ruby, emerald, sapphire, and other well-known gem stones.

GOLD-QUARTZ--in crystals, filiform, reticulated, and arborescent shapes--is commonly worn as a jewel. Gold penetrating white, black, rose, and amethystine quartz, is worked into jewelry of all sorts, sometimes of very elaborate designs. These uses of gold-quartz are most common on the Pacific coast and in western North American cities.

HEMATITE, composed of iron 70, oxygen 30, is commonly cut into beads, charms, and intaglios. Chromic iron and ilmenite are similarly used. Although this iron ore is steel-grey, when polished, its streak, when scratched, is red; hence the name hematite, meaning "bloodstone."

IOLITE, also called dichroite and water sapphire, is a pleochroic mineral occasionally cut for gem purposes. It is somewhat harder than quartz.