_Crystalline System_: Rhombohedral. _Hardness_: 7. _Lustre_: Vitreous. Splendent to dull and resinous. _Refraction_: Double. _Chemical Composition_: Silicon 46.67. Oxygen 53.33. _Chemical Symbol_: SiO_{2}. _Specific Gravity_: 2.5-2.8. In pure crystals 2.65. _Dichroism_: Distinct. _Properties_: Generates positive electricity by friction. It is infusible under the blowpipe, but effervesces with Carbonate of Soda. Although it resists the common acids it may be dissolved in Hydrofluoric. _In the Zodiac_: Rock Crystal is under the Heavenly Pisces; Amethyst is under the Heavenly Aries; Cairngorm under the Heavenly Scorpio; Chrysoprase under the Heavenly Cancer; Catseye under the Heavenly Capricorn; Plasma under the Heavenly Virgo; Jasper under the Heavenly Virgo; Bloodstone under the Heavenly Leo; Camelian under the Heavenly Leo; Agate under the Heavenly Scorpio; Onyx under the Heavenly Capricorn; Sardonyx under the Heavenly Leo; Moss Agate under the Heavenly Taurus. _Where found_: Distributed plentifully about the world. Rock Amethyst is found in the United States, Brazil, India, Ceylon, Ekaterinburg, Australia, etc. Mr. R. J. Dunn, late Victorian Geologist, discovered large quantities of Rose Quartz in South Africa. It is also found in the United States, Russia, Australia and other places. Catseyes are found in Ceylon and India. Cairngorm is found in Scotland, United States, Australia, etc. Chrysoprase is found in the United States and other places. SPINEL SPINEL RUBY, BALAS RUBY, RUBICELLE, PLEONASTE OR CEYLONITE _Crystalline System_: Isometric. _Hardness_: 8-8½. _Lustre_: Vitreous. _Refraction_: Single. _Chemical Composition_: Alumina 72. Magnesia 28. _Chemical Symbol_: MgAl_{2}O_{4}. _Specific Gravity_: 3.5-4.0. _Dichroism_: None. _Properties_: Does not display electricity when submitted to friction or heat, but under heat the red spinel changes to brown. On cooling it becomes green, after which it is nearly colourless; then it resumes its pristine hue. Spinel crystals also change into Hydrotalcite, a soft pearl-like stone of similar chemical composition. Infusible alone under the blowpipe but yields slowly with Borax. It is soluble in concentrated Sulphuric Acid. _In the Zodiac_: Spinel, Balas, Almandine, Ruby and Sapphirine are under the Heavenly Virgo. The Chloro-Spinel and the Pleonaste are under the Heavenly Capricorn. _Where found_: United States, Canada, Burma, Siam, Ceylon, Australia, etc. It is discovered in granular limestone, in gneiss and rocks of volcanic origin. SPODUMENE KUNZITE—HIDDENITE