Different types of blue gemstones

Search the internet for ‘blue gemstones’ and you will find a list of at least 33 stones ranging in alphabetical order from agate to zircon, but from these you might only recognise six or seven. In our June 2007 issue we featured 20 gems which had blue as the dominant colour.

Not all blue gemstones are the same

In this article we will feature the most commonly recognised of these stones in order of the ‘hardness’ (or wearability) – in other words those most suitable for jewellery. The globally recognised system of measuring gemstone hardness is known as the Mohs’ scale (named after Friedrich Mohs, a mineralogist who invented a scale of hardness based on the ability of one mineral to scratch another.

There are ten minerals in Mohs scale, from the ‘softest (1)talc, (2)gypsum, (3)calcite, (4)fluorite, (5)apatite, (6)feldspar, (7)quartz, (8)topaz, (9)corundum, to the hardest, (10)diamond.

Here are some of the most common gemstones:

Sapphire  (9.0)  the richest, saturated blue

Ceylon sapphire                                           Australian sapphire

Blue is by far the most popular colour for sapphires, but they can be almost any colour, including yellow, green, white, colourless, pink, orange, brown and purple.

Topaz (8.0)    translucent, from very light to medium blue

London blue topaz                                  Swiss blue topaz

The two most popular treated topaz. Swiss Blue is bright blue with a light tone and light to moderate saturation. London Blue is dark blue with a moderate to dark tone and saturation.

Aquamarine (7.5 – 8.0)   light translucent blue

Aquamarine is a member of the beryl family  (which includes emerald) and ranges in colour from an almost colourless pale blue to blue-green. The most prized colour is a deep-blue aqua.

 Zircon (7.5)    medium to dark translucent blue

Zircon is routinely heat treated. This has two effects on the gem: It alters the colour to colourless, blue or golden (the most preferred colours for zircon) and orange to red colours.

Tourmaline  (7.0 – 7.5)      shades of light to dark blue

Found in Brazil, Sri Lanka, Afghanistan, Nigeria, Kenya and in the USA. This variety of tourmaline comes in various shades, including a clear blue colour.

Compared to the other varieties, the blue stone is quite rare.

Tanzanite (6.0 – 6.5)    dark translucent violet blue

First discovered in 1967 in Tanzania, East Africa. It is part of the zoisite mineral species and is only found in East Africa. Tanzanite is very rarely a pure blue and usually exhibits rich purple overtones.

Lapis Lazuli (5.0 – 5.5)   medium rich blue

Sometimes with a hint of violet. Its value decreases with the presence of white patches (calcite), while small veins of pyrite are often prized.

Spinel  (8.0)     translucent medium violet-blue

A favourite of gem dealers and collectors on account of its brilliance, hardness and wide range of spectacular colours. Beautiful blue tones, called cobalt spinel are very rare.

Agate  (7.0)     a soft blue

Variety of chalcedony formed from layers of quartz that usually show vari-coloured bands.

Design your own blue gemstone jewellery

With many a blue gemstone to choose from the possibilities are endless. Whether it be designing an item of jewellery from scratch or simply purchasing a loose gemstone for your collection, let us help you design the heirloom piece of your dreams. Contact us today to make a no obligation appointment and select your favourite coloured gemstone. 03 9650 3830. info@abrecht.com.au