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A sand grain of volcanic glass under the petrographic microscope. Its amorphous nature makes it go extinct in cross-polarized light (bottom frame), and thus does not have an extinction angle. Scale box in millimeters. Undulose extinction in quartz.
These lenses are used for UV photography, as the quartz glass can be transparent at much shorter wavelengths than lenses made with more common flint or crown glass formulas. Fused quartz can be metallised and etched for use as a substrate for high-precision microwave circuits, the thermal stability making it a good choice for narrowband filters ...
Egyptian faience is a sintered-quartz ceramic material from Ancient Egypt. The sintering process "covered [the material] with a true vitreous coating" as the quartz underwent vitrification, creating a bright lustre of various colours "usually in a
Vitreous minerals have the lustre of glass. (The term is derived from the Latin for glass, vitrum.) This type of lustre is one of the most commonly seen, [9] and occurs in transparent or translucent minerals with relatively low refractive indices. [2] Common examples include calcite, quartz, topaz, beryl, tourmaline and fluorite, among others.
Sand is a common source for silica. For certain types of glass, the Murano glassmakers used quartz as their source for silica. Quartz pebbles were crushed into a fine powder. Two sources for sand were Crete and Sicily. Quartz pebbles were selected from the Ticino and Adige rivers in Northern Italy. [68]
Quartz porphyry from the island of Alnö, Sweden. Phenocrysts of clear glassy rounded quartz and white orthoclase feldspar are set in a fine-grained matrix. Sample is just over 10 cm long. Quartz-porphyry, in layman's terms, is a type of volcanic rock containing large porphyritic crystals of quartz.