Natural Grandidierite
Grandidierite is a magnesium aluminum borosilicate (simplified MgAl3(BO3)(SiO4)O2) with a blue-green to teal color, sometimes closer to sea green. It is one of the rarer gem species, found almost exclusively in Madagascar. With a Mohs hardness of about 7.5 it is durable enough for jewelry, and its most remarkable trait is its strong pleochroism.
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Natural Grandidierite 5.32ct Cushion Cut
€77.00 EURNatural Grandidierite 1.55ct Oval Cut
€41.00 EUR
Gemstone guide
Natural Grandidierite
About grandidierite
Grandidierite was first described in 1902 from southern Madagascar and named after the French explorer and naturalist Alfred Grandidier, who studied the island's natural history. For most of the twentieth century it was known only as opaque material, and transparent, gem-quality crystals were found in Madagascar much later, which is why faceted grandidierite is still uncommon. Madagascar remains its primary source, and it is not treated.
Did you know?
The first known transparent faceted grandidierite was a stone of just 0.29 carats, cut from rough reportedly found in Sri Lanka and described in 2003.
A new deposit found near Tranomaro in Madagascar around 2014 brought more gem material to the market. Facetable crystals are known only from Madagascar and Sri Lanka.
How to recognise grandidierite
Grandidierite is strongly trichroic: the same crystal can show dark blue, blue-green and near-colorless white depending on the angle you view it from, a hallmark that helps confirm genuine material. Its blue-green is usually soft and slightly greyish, and many stones contain fine fibers or fluid inclusions.
Caring for grandidierite
Grandidierite is hard but has a good cleavage, so protect it from sharp knocks. Clean it with warm soapy water and a soft brush, and avoid ultrasonic and steam cleaners.
Every stone is natural, and each listing gives its weight, size, origin and treatment, with photos of the actual stone.