Agate
| Agate |
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 Moss agate pebble, 2.5 cm (1 inch) long |
| General |
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| Category | Quartz variety |
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| Chemical formula | Silica, SiO2 |
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| Identification |
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| Color | White to grey, light blue, orange to red, black. |
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| Crystal habit | Cryptocrystalline silica |
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| Crystal system | Rhombohedral Microcrystalline |
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| Cleavage | None |
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| Fracture | Conchoidal with very sharp edges. |
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| Mohs scale hardness | 7 |
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| Luster | Waxy |
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| Streak | White |
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| Specific gravity | 2.58-2.64 |
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| Refractive index | 1.530-1.540 |
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| Birefringence | up to +0.004 (B-G) |
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| Pleochroism | Absent |
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Agate