Carnelian
From Wikipedia, the free encyclopedia
| Carnelian | |
|---|---|
.jpg/250px-Carnelian_sard_(mineral_specimen).jpg) Polished carnelian pebbles. Scale is in millimeters.
|
|
| General | |
| Category | Chalcedony variety |
| Chemical formula | Silica (silicon dioxide, SiO2) |
| Identification | |
| Molecular Weight | 60 g / mol |
| Color | Reddish-brown |
| Crystal system | Trigonal |
| Cleavage | Absent |
| Fracture | Uneven, splintery, conchoidal |
| Mohs Scale hardness | 6 - 7 |
| Luster | Vitreous, dull, greasy, silky |
| Streak | White |
| Specific gravity | 2.59 - 2.61 |
| Diaphaneity | Translucent |
| References | [1] |
Carnelian, sometimes spelled cornelian, is a red or reddish-brown variant of chalcedony. Similar to carnelian is sard, which is generally harder and darker.
Contents |
[edit] Distinction between carnelian and sard
The words carnelian and sard are often used interchangeably, but they can also be used to describe distinct subvarieties. The purported differences are as follows:
| Carnelian | Sard | |
|---|---|---|
| Colour | Lighter, with shades ranging from orange to reddish-brown. | Darker, with shades ranging from a deep reddish-brown to almost black. |
| Hardness | Softer | Harder and tougher. |
| Fracture | Uneven, splintery and conchoidal | Like carnelian, but duller and more hackley. |
It should be noted that all of these properties vary across a continuum, and so the boundary between carnelian and sard is inevitably blurred.
[edit] History
Carnelian was used widely during Roman times 2,000 years before the present era to make signet or seal rings for imprinting a seal with wax on correspondence or other important documents. Hot wax does not stick to Carnelian. [2]
The word carnelian is derived from the Latin word meaning horn, in reference to the flesh color sometimes exhibited.
[edit] Folklore
Carnelian is the zodiac birthstone of Virgo according to some texts. It is also one of the gemstones (along with peridot, diamond and sapphire) that has been associated with the month August.
[edit] See also
[edit] References
- ^ Rudolf Duda and Lubos Rejl: Minerals of the World (Arch Cape Press, 1990)
- ^ Section 12 of the translation of Weilue - a 3rd century Chinese text by John Hill under "carnelian" and note 12.12 (17)
[edit] External links
|
|||||||||||||||||
|
||||||||||||||||||||||||||||
