Quartz facts for kids
Quick facts for kids Quartz |
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Quartz crystal cluster from Tibet
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| General | |
| Category | oxide mineral |
| Formula (repeating unit) |
SiO2 |
| Strunz classification | 4.DA.05 (Oxides) |
| Dana classification | 75.01.03.01 (tectosilicates) |
| Unit cell | a = 4.9133 Å, c = 5.4053 Å; Z=3 |
| Identification | |
| Color | Colorless through various colors to black |
| Crystal habit | 6-sided prism ending in 6-sided pyramid (typical), drusy, fine-grained to microcrystalline, massive |
| Crystal system | α-quartz: trigonal β-quartz: hexagonal |
| Twinning | Common Dauphine law, Brazil law and Japan law |
| Cleavage | {0110} Indistinct |
| Fracture | Conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 7 – lower in impure varieties (defining mineral) |
| Luster | Vitreous – waxy to dull when massive |
| Streak | White |
| Diaphaneity | Transparent to nearly opaque |
| Specific gravity | 2.65; variable 2.59–2.63 in impure varieties |
| Optical properties | Uniaxial (+) |
| Refractive index | nω = 1.543–1.545 nε = 1.552–1.554 |
| Birefringence | +0.009 (B-G interval) |
| Pleochroism | None |
| Melting point | 1670 °C (β tridymite) 1713 °C (β cristobalite) |
| Solubility | Insoluble at STP; 1 ppmmass at 400 °C and 500 lb/in2 to 2600 ppmmass at 500 °C and 1500 lb/in2 |
| Other characteristics | lattice: hexagonal, Piezoelectric, may be triboluminescent, chiral (hence optically active if not racemic) |
Quartz is the second most common mineral in Earth's continental crust. Its crystal structure is a framework of SiO4 silicon–oxygen tetrahedra. Each shares an oxygen atom oxygen with another tetrahedron, so the overall chemical formula is SiO2 or silica.
There are many different varieties of quartz, some of which are semi-precious gemstones. Varieties of quartz have been used for a long time in the making of jewelry and hardstone carving. Agate, amethyst, rose quartz are all forms of quartz.
Quartz is a component used to make quartz clocks. Sand often has a lot of small quartz bits. This mineral contains silica. Quartz has a mineral hardness of 8. (mohs scale).
The word "quartz" comes from the German word "quarz".
'Fused quartz' is glass made of silica in non-crystalline form. It does not contain other ingredients. These are usually added to glass to lower the melt temperature. Fused silica has high working and melting temperatures. The properties of fused quartz are superior to those of other types of glass due to its purity. The glass is used in a number of high-tech products.
Images for kids
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Quartz crystal demonstrating transparency
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A synthetic quartz crystal grown by the hydrothermal method, about 19 cm long and weighing about 127 grams
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Granite rock in the cliff of Gros la Tête on Aride Island, Seychelles. The thin (1–3 cm wide) brighter layers are quartz veins, formed during the late stages of crystallization of granitic magmas. They are sometimes called "hydrothermal veins".
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Herkimer diamond
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Rock crystal
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Ametrine
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Amethyst
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Blue quartz
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Chalcedony
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Citrine
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Rose quartz
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Prasiolite
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Rutilated quartz
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Sceptred quartz
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Smoky quartz
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Rock crystal jug with cut festoon decoration by Milan workshop from the second half of the 16th century, National Museum in Warsaw. The city of Milan, apart from Prague and Florence, was the main Renaissance centre for crystal cutting.
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Synthetic quartz crystals produced in the autoclave shown in Western Electric's pilot hydrothermal quartz plant in 1959
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Fatimid ewer in carved rock crystal (clear quartz) with gold lid, c. 1000.
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See also
In Spanish: Cuarzo para niños
