Crystal and stones » fire opal

Red and rose gemstones

precious stones — Wed, 16 Sep 2009 15:11:03 +0000

Red and rose gemstones

Hardness. Specific Gravity.

Carnelian (a variety of Chalcedony) 6-1/2 2.598-2.610 Diamond 10 3.502-3.564 Deep Red Garnet 7-1/4 3.40-4.50 Jasper 7 2.668 Opal (the “Fire Opal”) 5-1/2-6-1/2 2.21 Ruby 9 4.073-4.080 Rhodonite 5-1/2-6-1/2 3.413-3.617 Sapphire 9 4.049-4.060 Spinel Ruby 8 3.614-3.654 Topaz 8 3.500-3.520 Tourmaline 7-1/4 3.024 Zircon 7-1/2 4.70-4.88

Hauynite to Opal

precious stones — Wed, 16 Sep 2009 14:18:50 +0000

Group F. -Stones whose specific gravity lies between 2.00 and under 2.50.

Hauynite 2.470 and occasionally to 2.491 Lapis lazuli 2.461 Moldavite 2.354 Opal 2.160 and according to variety to 2.283 Opal (Fire Opal) 2.210 (average)

Specific gravity of gemstones

precious stones — Wed, 16 Sep 2009 13:53:09 +0000

The fixing of the specific gravity of a stone also determines its group position with regard to weight; its colour and other characteristics defining the actual stone.

This is a safe and very common method of proving a stone, since its specific gravity does not vary more than a point or so in different [...]

Pleochroism and colour of minerals

precious stones — Wed, 16 Sep 2009 13:13:11 +0000

Color is one of the most wonderful effects in nature. It is an attribute of light and is not a part of the object which appears to be coloured; though all objects, by their chemical or physical composition, determine the number and variety of vibrations passed on or returned to the eye, thus fixing their [...]