Crystal and stones » Classification of gems

Magnetic and Electric Influences

precious stones — Wed, 16 Sep 2009 14:35:43 +0000

The word “electricity” is derived from the Greek “elektron,” which was the name for amber, a mineralised resin of extinct pine-trees. It was well-known to the people of pre-historic times; later to the early Egyptians, and, at a still later date, we have recorded how Thales -the Greek philosopher, who lived about the close of [...]

Heat-rays to precious stones

precious stones — Wed, 16 Sep 2009 14:30:16 +0000

Another method of isolating certain stones is by the action of heat-rays.

Remembering our lessons in physics we recall that just as light-rays may be refracted, absorbed, or reflected, according to the media through which they are caused to pass, so do heat-rays possess similar properties.

Therefore, if heat-rays are projected through precious [...]

Jet to Amber

precious stones — Wed, 16 Sep 2009 14:19:31 +0000

Group G. -Stones whose specific gravity is under 2.00.

Jet 1.348 Amber 1.000

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)

Phenakite to Rock-crystal

precious stones — Wed, 16 Sep 2009 14:17:44 +0000

Group E. -Stones whose specific gravity lies between 2.50 and under 3.000.

Phenakite 2.965 Turquoise 2.800 Beryl 2.709 and occasionally to 2.81 Aquamarine 2.701 ” 2.80 Labradorite 2.700 Emerald 2.690 Quartz 2.670 Chrysoprase 2.670 Jasper 2.668 Amethyst 2.661 Hornstone 2.658 Citrine 2.658 Cordierite 2.641 Agate 2.610 Chalcedony 2.598 and occasionally to 2.610 Adularia 2.567 Rock-crystal [...]

Rhodonite to Nephrite

precious stones — Wed, 16 Sep 2009 14:15:37 +0000

Group D. -Stones whose specific gravity lies between 3 and under 3.50.

Rhodonite 3.413 and occasionally to 3.617 Garnets 3.400 ” 4.500 Epidote 3.360 ” 3.480 Sphene 3.348 and occasionally to 3.420 Idocrase 3.346 ” 3.410 Olivine 3.334 ” 3.368 Chrysolite 3.316 ” 3.528 Jade 3.300 ” 3.381 Jadeite 3.299 Axinite 3.295 Dioptase 3.289 Diopside [...]

Pyrope to Diamond

precious stones — Wed, 16 Sep 2009 14:13:01 +0000

Group C. Stones whose specific gravity lies between 3.50 and under 3.70.

Pyrope (average) 3.682 Chrysoberyl 3.689 and occasionally to 3.752 Spinel 3.614 ” 3.654 Kyanite 3.609 ” 3.688 Hessonite 3.603 ” 3.651 Diamond 3.502 ” 3.564 Topaz 3.500 ” 3.520

Garnets to Malachite

precious stones — Wed, 16 Sep 2009 14:11:33 +0000

Group A. Isolates gems with a specific gravity of 4.7963 and over 4.70; in this group is placed zircon, with a specific gravity of from 4.70 to 4.88.

Group B. Stones whose specific gravity lies between 3.70 and under 4.7963.

Garnets, many varieties. Almandine 4.11 and occasionally to 4.25 Ruby 4.073 ” 4.080 Sapphire 4.049 [...]

Seven solutions

precious stones — Wed, 16 Sep 2009 14:08:49 +0000

Beginning then with the pure double nitrate of silver and thallium, this will isolate the stones of less specific gravity than 4.7963, and taking the lighter solutions and standardising them, we may get seven solutions which will isolate the stones as follows:

A shows the stones which have a specific gravity over 4.7963 B ” [...]

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 [...]