Lapis Lazuli
Lapis Lazuli is composed of several minerals in addition to Lazurite, including agate, calcite, diopside, enstatite, mica hauynite, hornblende, nosean, sodalite and pyrite - it is considered to be not a mineral but a rock. Lapis is Latin for 'Stone'.The name of bath lazuli and Lazurite are derived from the Persian 'blue' or 'heaven'. The Lapis lazuli name often shortened to Lapis, is sometimes mistakenly used for the mineral Lazurite. The ancient Egyptians used it extensively in religious ceremonies, and lapis item were found in the tomb of Tutan Khamen. It was a popular stone in Mesopotamia. The Greeks and Romans used it as a reward of bravery. In the 17th century it was used in medicine to prevent miscarriages, epilepsy and dementia.
The value of lapis lazuli is largely determined by the abundance and colour of the dark intense blue lazurite. The colours range from greenish-blue to purple-blue. The fleckes of gold pyrite and white calcite can often increase the value of it.
|
|
|
|
DEPOSIT
The finest qualities of Lapis are found in the West Hindu Kush mountains in Afghanistan. Russian deposits are at the south west end of lake Baikal. Chile's deposits are north of Santiago. Other deposited are found in Angola, Burma, Canada, Pakistan, California and Colorado.
PROPERTIES
| Species | LAPIS LAZULI |
| Variety | Lapis Lazuli |
| Chem. System | Granular rock composed of lazurite, hauynite, sodalite, noselite, varying amounts of pyrite inclusions with calcite in a mottled or vein like pattern, diopside may also be present. |
| Cryst. System | Rock, mixture of minerals present therefore no crystal system |
| Habit | Aggregate |
| Colour | Blue, greenish to purple blue. |
| Cause of Colour | Blue - Sulfur related colour centers. |
| Transparency | Semi - translucent to opaque |
| Luster | Vitreous to greasy |
| Hardness | 5.5 |
| S . G | 2.80 ( 2.7 to 2.9) higher when pyrite is present |
| Cleavage | None |
| Fracture | Granular to uneven |
| SR/DR | SR/AGG |
| Pleochroism | None |
| Optic Sign | None |
| Optic Char | None |
| R.I. Range | 1.50 (Mean) |
| Birefringence | None |
| Spectrum | None Characteristic |
| U . V. Light | Whitish glow, orange streaks in some. |
INCLUSION
Inclusion found in Lapis Lazuli are Iron, Pyrites & Calcite.
SIMULANTS
Swiss lapis, synthetic sintered spinel, paste with copper, sodalite, dyed chalcedony, Gilson imitation lapis lazuli.
|
|
|
|
|
|
|
|
