Amber

Amethyst

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Aragonite

Aventurine

Azurite

Carnelian

Citrine

Connemara Marble

Emerald

Fluorite

Garnet

Hemetite

Imperial Topaz

Iolite

Jade

Jasper

Kunzite

Labradorite

Lapis lazuli

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Malachite

Moldavite

Moonstone

Moss agate

Peridot

Quartz Crystal

Rose Quartz

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Zircon

Iolite

Iolite is gem quality Cordierite (Magnesium Aluminum Silicate) a blue silicate mineral that occurs as crystals or grains in igneous rocks as a result of contamination of the magma by aluminous sediment.
It is extremely pleochroic, which means it appears as different colors depending upon which direction the stone is viewed. Iolite has three pleochroic directions. In one direction, it appears blue, in another bluish gray and in the other grayish yellow.

Iolite is also known as the Vikings' compass, due to it's ability to determine the direction of the sun on overcast days. When the legendary Viking mariners sailed the wide ocean, they used thin pieces of iolite as the world's first polarizing filter. Looking through an iolite lens, they could determine the exact position of the sun, on clouded, foggy days or when the sun had just set.and navigate safely. This works by determining the direction of polarization of the sky over head. Light scattered by air molecules is polarized, and the direction of the polarization is at right angles to a line to the sun, even when the sun's disk itself is obscured by dense fog or lies just below the horizon.

First, (iolite) is set in the position where the colour of the gemstone is the deepest or darkest. This is achieved by rotation and by turning of (the stone). Now we see two rays coming from (the mineral) – the vibration direction of the darker ray is parallel to the polarized ray coming directly from sun to the eye and has strong intensity. Any movement of (the iolite) from this direct line would result in the change of colour of (the stone) – it is getting lighter – the colorless or lighter component is getting stronger because light is not so well polarized. With small movements – left and right and up and down but keeping the stone in the same orientation – we can find the direct line to the sun hidden behind clouds.