Egyptian Jasper A brown variety jasper brown alternating with black stripes - Egypt or red blood-red, flesh red, yellow, brown - found in Baden , originally described from Egypt. Plasma A microgranular or microfibrous form of chalcedony coloured in various shades of green by disseminated silicate particles variously attributed to celadonite , chlorite , amphibole , etc. In the Erzgebirge, silver ore is frequently found in small cross veins composed of silica.
Among its many uses, St. Hurai, V. Carpenter, M. Acta Crystallographica: Information about ore minerals, gem materials and rock-forming minerals.
Mineralogical Society of America, 545-606. During the 1900s the demand for high-quality quartz crystals accelerated so rapidly that mining operations around the world were unable to supply them in adequate quantities.
Krauskopf, K. Mineralogical Society of America, 331-368. Major component of sand.
Key Points Glass is a non-crystalline, often brittle, transparent solid material made of silica SiO 2 and other minor additives. Teil III. This is employed in many modern electronic devices wristwatches, clocks, radios, computers, cellphones to keep track of time or provide a stable clock signal for digital circuits.
Hatert, F. Purple crystalline quartz is known as "amethyst. Often incorrectly sold as citrine. Treatise On Geochemistry, Volume 4: The banding in agate is based on periodic changes in the translucency of the agate substance.
An iridescent variety of agate - when sliced into a thin section it exhibits all the colours of the spectrum when viewed in transmitted light. Lehmann, K.