Agate
Agate is a kind of quartz and it is a mineral. Agate can come in many different kinds and colors. Agate deposits are primarily found in large rocks such as boulders. They take ~50 million years to form. It is characterized by colored band patterns inside various rocks. Often, agates are also accompanied by Amethyst deposits inside.[1]
| Agate | |
|---|---|
 Moss agate pebble, 2.5 cm (1 inch) long | |
| General | |
| Category | Quartz variety |
| Formula (repeating unit) | Silica, SiO2 |
| Identification | |
| Color | White to grey, light blue, orange to red, black. |
| Crystal habit | Cryptocrystalline silica |
| Crystal system | Rhombohedral Microcrystalline |
| Cleavage | None |
| Fracture | Conchoidal with very sharp edges. |
| Mohs scale hardness | 7 |
| Luster | Waxy |
| Streak | White |
| Specific gravity | 2.58-2.64 |
| Refractive index | 1.530-1.540 |
| Birefringence | up to +0.004 (B-G) |
| Pleochroism | Absent |
Agate Media
Faceted Botswana agate
Agate drinking horn, Tang dynasty
A 6.8 kg (15 lb) barrel full of tumble-polished agate and jasper
Gold Roman signet ring with portrait of emperor Commodus in niccolo agate, 180-200 CE, found in Tongeren, Gallo-Roman Museum (Tongeren)
The "Rubens Vase" (Byzantine Empire). Carved in high relief from a single piece of agate, most likely created in an imperial workshop for a Byzantine emperor.
Victorian banded agate earrings
Maryland Agate - Cut and illuminated to show internal structures
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References
- ↑ Streeter, Edwin W. (2014-07-07). Semi-Precious Stones - A Historical Article on Agate, Amber, Amethyst and Many Other Varieties of Gemstones. Read Books Ltd. ISBN 978-1-4733-9436-0.