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Chemical Formula: Mg2Al3O
Mineral Name: Iolite
Color: Transparent, violet-blue, light blue,
blue, rich blue-violet stone
Hardness: 7.5
Iolite is a silicate of alumina, iron, and magnesia,
having a bright blue color and vitreous luster;
cordierite. The name iolite comes from the Greek ios,
which means violet. Iolite is a blue silicate mineral
that occurs as crystals or grains in igneous rocks,
only as a result of contamination of the magma by
aluminous sediment. The property that made iolite so
valuable to the Vikings is extreme pleochroism. Iolite
has different colors in different directions in the
crystal. The gemstone changes colors depending upon
which angle it is viewed from.
Iolite, 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, and navigate safely.
Synthetic magnesium iolite has a low thermal expansion
and is used as a semirefractory material because of
its resistance to thermal shock. Iolite is
artistically used in making necklaces, pendants,
rings, bracelets etc. Iolite is commonly cut into
traditional shapes, and its most desirable color is a
rich violet-blue. It is found in the regions of Sri
Lanka, Burma, India, Madagascar and Brazil.
