Gold Sheen Sapphire is different to other precious gemstones, while three of the ‘4 C’s’ – cut and carat size and colour, apply, clarity is all but irrelevant. In some respects, Gold Sheen Sapphire is similar to opal, it is an opaque gem where the colour is a feature of different types of mineral inclusion. However Gold Sheen Sapphire also retains the properties of sapphire, and often the predominant colour is blue, clear, or fancy sapphire.
These are some tips of what to look for and what to avoid when buying Gold Sheen Sapphire:
- Surface Flaws – the lustre of Gold Sheen Sapphire is a major factor in the beauty of the gem. Stones should have an eye clean surface. Comparing two similar pieces with a 10x loupe will show that the better the surface the greater the appeal of the gem.
- Structural Flaws – as with any gemstone, cracks through the stone can cause problems with durability and jewellery setting. However it is important not to mistake geometric and inclusion features of the gem as a structural flaw. Generally this is obvious though, with closer inspection.
- Asterism – All Gold Sheen Sapphire cabs will display some degree of asterism. It will vary from very weak to strong, but it will be there. Strong aterism is quite rare.
- Vary the light – look at the gem under warm and cool light, and in daylight if possible. I am not sure if this should be classed as ‘colour change’, but the visual difference under different lighting types will be quite pronounced.
- Geometric Patterns – One, if not the, most beautiful feature of Gold Sheen Sapphire are the naturally occurring geometric patterns. These are most evident as parallel lines, partial or full hex patterns, often interlaced with clear or coloured sapphire. These patterns made every Gold Sheen Sapphire absolutely unique, like a highly prominent fingerprint. Partial hex patterns are rare, and the fuller the hex, the rarer the occurrence. Full hex patterns are very, very rare, occurring in less than one in 100,000 pieces.
- Craze lines – not to be mistaken with structural flaws, craze lines are small fractured that are usually between 70 and 120 degrees to the crystal growth lines. They have no structural impact on the gem.
- Aurora Effect – in addition to the sheen effect, some stones will have a combination of green and blue colour that will change as light plays across the gem Tanzim Khan (the discoverer of Gold Sheen Sapphire) calls this an ‘Aurora’ effect, because the colour effect is not unlike the Aurora Borealis. I am not sure if this is a new feature or a type of iridescence, but in any event., stones that exhibit this are very rare. You can see an example of the effect in this Youtube video – https://youtu.be/XCjCiT3q2TM
- Colours – The primary colours of corundum in Gold Sheen Sapphire are blue, white, yellow, green, orange, red. The metallic colours are gold, brass, bronze and copper. The following table lists the colours and their occurrence:
|Primary Colour||Metallic Colour||Other Features||Rarity|
|Blue||Under 20 carats||Common|
|Yellow||Bronze||Prominent blue/metallic banding||Uncommon|
|20 to 40 carats||Uncommon|
|40 to 60 carats||Rare|
|Orange||Full Hex clear window||Very Rare|
|Red||Over 60 Carats||Very Rare|