Mindblown: a blog about philosophy.

CASSITERITE THOUGH usually opaque, this oxide of tin, corresponding to the formula SnO2, has occasionally, but very rarely, been found in small, transparent, yellow and reddish stones suitable for cutting. The lustre is adamantine. The refraction is uniaxial in character and positive in sign, the ordinary index being I.997 and extra-ordinary 2.093. The specific gravity […]

ENSTATITE (`Green Garnet’) THE small green stones which accompany the diamond in South Africa have been cut and put on the market as ` green garnet.’ They are, however, in no way connected with garnet, but belong to a mineral species called enstatite, which is a silicate of magnesium corresponding to the formula MgSiO3 ; […]

EUCLASE THIS species comes near beryl in chemical composition, being a silicate of aluminium and beryllium corresponding to the formula Be(AIOH) SiO4, and closely resembles aquamarine in colour and appearance when cut. Owing to the rarity of the mineral good specimens command high prices for museum collections, and it is seldom worth while cutting it […]

(Kunzite, Hiddenite) TILL a few years ago scarcely known out-side the ranks of mineralogists, spodumene suddenly leaped into notice in 1903 upon the discovery of the lovely lilac-coloured stones (Plate XXIX, Fig. 1o) at Pala, San Diego County, California ; they shortly afterwards received the name kunzite after the well-known expert in gems, Dr. G. […]

THOUGH not usually accounted precious among European nations or in Western civilization in general, jade was held in extraordinary esteem by primitive man, and was fashioned by him into ornaments and utensils, often of considerable beauty, and even at the present day it ranks among the Chinese and Japanese peoples above all precious stones ; […]

DIAMOND has held pride of place as chief of precious stones ever since the discovery of the form of cutting known as the ‘ brilliant’ revealed to full perfection its amazing qualities ; and justly so, since it combines in itself extreme hardness, high refraction, large colour-dispersion, and brilliant lustre. A rough diamond, especially from […]

OF all the opaque stones turquoise (Plate XXIX, Fig. 17) alone finds a prominent place in jewellery and can aspire to rank with the precious stones. The colour varies from a sky-blue or a greenish blue to a yellowish green or apple-green. Only the former tints, which are at the same time the rarer, are […]

(Moonstone, Sunstone, Labradorite, Amazon-Stone) THOUGH second to none among minerals in scientific interest, whether regarded from the point of view of their crystalline characters or the important part they play in the formation of rocks, the group included under the general name felspar occupies but a humble place in jewellery. It consists of three distinct […]

( White Opal, Black Opal, Fire-Opal) THAT opal in early times excited keen admiration is evident from Pliny’s enthusiastic description of these stones : ” For in them you shall see the burning fire of the carbuncle, the glorious purple of the amethyst, the green sea of the emerald, all glittering together in an incredible […]

CHALCEDONY and agate, and their endless varieties, are composed mainly of silica, but the separate individual crystals are so small as to be invisible to the unaided eyesight, and occasion-ally are so extremely minute that the structure is almost amorphous. The colour and appearance vary greatly, depending upon the impurities contained in the stone, and, […]