materials science
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Acicular
Acicular, in mineralogy, refers to a crystal habit composed of slender, needle-like crystals. Crystals with this habit tend to be fragile. Complete, undamaged acicular specimens are uncommon. The term “acicular” derives from the Late Latin “acicula” meaning “little needle”. Strictly speaking, the word refers to a growth habit that is slender and tapering to a point. Prismatic crystals are not acicular; however,…
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Wood Opal
Wood opal is a form of petrified wood which has developed an opalescent sheen or, more rarely, where the wood has been completely replaced by opal. Other names for this opalized sheen-like wood are opalized wood and opalized petrified wood. It is often used as a gemstone. References
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Chert
Chert is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood. Chert is typically composed of the petrified remains of siliceous ooze, the biogenic sediment that covers large areas of the deep ocean floor, and which contains the silicon…
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Galvanic anti-neuralgic headband made up of a series of 24 alternate zinc and copper discs mounted onto a felt and ribbon band. The headband was tied around the head, with the discs resting on the temples, where perspiration would act on the discs by producing a mild galvanic current
Galvanic anti-neuralgic headband made up of a series of 24 alternate zinc and copper discs mounted onto a felt and ribbon band. The headband was tied around the head, with the discs resting on the temples, where perspiration would act on the discs by producing a mild galvanic current