FAQ on gemstones

FAQ still under construction!

What classifies as a "gemstone"?

In the past stones that were unusally beautiful due to their attributes like their colour and transparency were called gemstones. The exact definitions have varied over the course of history, but this is the modern gemstone division system that is based on the Mohs' scale of hardness:

• Rare gemstones: Stones within 8 and 10 in the Mohs scale (diamonds, corundum (ie. sapphires and rubies) and topaz)
• Gemstones: Stones within 6 and 8 in the Mohs scale
• Semi-precious gemstones: Stones within 2 and 7 in the Mohs scale

A simpler division is based on the Mohs scale value 7: in this division, all stones with Mohs 7 or higher are considered gemstones, and stones below Mohs 7 are considered semi-precious gemstones.

What is the Mohs scale?

The Mohs scale is an ordinal scale of mineral hardness. The scale has ranges from 1 to 10 with 1 being the softest (talcum) and 10 the highest (diamond). Stones are attributed a Mohs value based on which stones they can scratch, and which stones can scratch them. More on the Mohs scale can be found here at Wikipedia.

Why is Mohs 7 a "divider value" in the simpler gemstone division system?

The air contains minuscule particles of quartz, which has a Mohs value of 7. Over time, stones with a Mohs value less than 7 will be dulled and dimmed by this quartz dust.

What is corundum?

Corundum is the name of a crystalline form of a aluminium oxide, a mineral. All rubies and sapphires are corundums: deep red corundums are called rubies, whereas the word "sapphire" is used for corundums of all other colours.

What factors contribute to the price of a certain gem?

The classic "4 C's" or

• Carats (the weight of the stone)
• Cut (the quality of the cut)
• Clarity (how inclusion-free the stone is)
• Colour (the hue and depth of the colour)

What is a carat?

A carat (abbreviated ct. or ca.) can mean a few different things depending on the context.

• When dealing with gemstones and pearls, carat is a weight unit; 1 carat = 0,2 grams
• When dealing with gold, carat is a measure of purity; 1 carat = 1/24 purity by weight

How are gemstones named?

This is a fascinating field of study. In the past stones were usually given names that described the appearance of the stone, for example ruby (from the latin ruber, or red). Nowadays stones are most commonly given names derived from the name of the place where the mineral was first found (such as Elbaite, from the Italian island of Elba) or the name of the founder of the mineral or the honour of another person.

Some interesting gemstone nomenclature origins:

• Padparascha, used to describe deep-yellow and orange sapphires: from the Sinhalese word for lotus flower
• Tourmaline: from the Sinhalese word turamali or "multi-coloured"
• Garnet: from the Latin word granatus meaning grain, probably a reference to the pomegranate fruit
• Hematite: from the Latin word haima meaning blood; haematite itself is dark gray in color but when scratched it leaves a red streak.
• Amethyst: from the Greek word amethuskein OR from the Latin word amethystos, meaning "not intoxicating": drinking alcohol from a cup fashioned out of amethyst was believed to ward off intoxication.

What is a cabochon gemstone?

A cabochon means a gemstone that has been shaped and polished. The top side of a cabochon is a dome, whereas the bottom side is flat. Opaque gems are often cut en cabochon instead of facetting.

What is a star ruby / star sapphire?

Star sapphires and rubies are cabochon-cut stones in which small needle-like inclusions composed of rutile quartz are aligned so that when the stone is viewed in a certain angle, an illuminated star pattern appears on top of the stone.