About SemiPrecious Stones: Benitoite, Cairngorm, Carnelian, Chondronite

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:

BENITOITE. A newly discovered gem mineral of California, blue in colour, and said, when selected crystals are cut in the right direction, to rival the sapphire in colour and to excel the blue corundum gem in brilliancy. The mineral is dichroic, the ordinary ray colourless, the extraordinary ray blue. Benitoite crystallises in the hexagonal system, trigonal division; its most common habit is pyramidal; cleavage, imperfect pyramidal; fracture, conchoidal to subconchoidal; hardness, 6 to 6 1/2; highly refractive. Benitoite fuses to a transparent glass at about 3. It is easily attacked by hydrofluoric acid. Chemically, benitoite is a very acid titanosilicate of barium. Benitoite was discovered in 1907 by Mr. Hawkins and T. Edwin Sanders in the Mt. Diabolo range near the San Benito-Fresno County line. The mineral was determined at the University of California, and is described in a bulletin of its geological department by George Davis Louderback and Walter C. Blasdale.

CAIRNGORM is the brown variety of rock crystal, also called "smoky topaz." Cairngorm has a sentimental and historic interest involved in its use as an ornament for the weapons and picturesque clan dress of the Scottish High-landers.

CARNELIAN is a reddish variety of chalcedony, merging into greyish red, yellow, and brown; it is translucent, like horn. Carnelian takes a high polish and its colours are sometimes heightened by exposure to the sun or by heat. This attractive semi-precious stone was formerly much more extensively used than now, and its merits may, through the vagaries of fancy and fashion, which govern the fates of all gems, again raise it higher in popular favour.