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Crystal Formation in Sapphire

There are two main types of gem rough sold – facet rough which is suited for gemstone cutting and specimen rough which may be less suitable for faceting but more valuable to a collector in its natural form.

3887d.JPGWhile our main priority is supplying good facet rough to gem cutters all around the world, we are always on the lookout for interesting pieces of interest to collectors.  In this post, we look at a few pieces which show interesting crystal formation.

The crystal system for sapphire is trigonal (or sometimes described as hexagonal-rhombohedral) usually with a prismatic habit.  Sapphires often occur as tapering hexagonal pyramids with a barrel-shaped form as in the above photograph.

The next series of photos show an interesting yellow patch inside a blue sapphire.  The left photo is a thin slice of an Australia sapphire (by Richard Hughes) – sourced from Figure 6 in an article by Richard Huges for AGTA GTC Lab Update May 17 2005.  The centre and right photos show similar examples found at the Aussie Sapphire mine in recent years (sapphires in their rough form, not sliced).

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The next couple of photos show some crystals fused together – both double and triple sapphire crystals – not suitable for faceting but interesting specimens.

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sl-crystal.jpgSapphires crystals from some sources often have deep horizontal striations on the prismatic faces as seen in this example from Sri Lanka (source: Mineral Miners).  We have not observed any of these types of sapphire crystals at our mine at Glen Innes (New England, NSW Australia).

The well-formed crystals shown below are more typical of the types found in our region and are referred to locally as “dog tooth” sapphires. They may have clearly defined prism faces as in the example on the left or be very smooth in form as in the example on the right.

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Hope you enjoyed this quick look at the wonderful variety to be found in sapphire – a great example of the fantastic world of gems and minerals.

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NOTE:  All photographs have been taken by Aussie Sapphire unless otherwise noted with a link to the source.