Corundum | Crystal and stones

Specific gravity of gemstones

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 [...]

Hardness is perhaps one of the most important features in a stone, especially those of the “gem” series, for no matter how colour, lustre, general beauty and even rarity may entitle a stone to the designation “precious,” unless it possesses great hardness it cannot be used as a gem or jewel.

Consequently, the hardness of [...]

Light and diaphaneity

Probably the most important of the many important physical properties possessed by precious stones are those of light and its effects, for to these all known gems owe their beauty, if not actual fascination.

When light strikes a cut or polished stone, one or more of the following effects are observed:–it may be transmitted through [...]