Characteristics and the extreme rarity of Grandidierite

One of the most magnificent qualities of Grandidierite other than its extreme rarity would have to be its colour of light blue neon saturation that can be compared to other world’s most valuable and most beautiful gemstones such as Paraiba tourmalines or crystal Blue apatite, however unlike these other 2 gemstones, Grandidierite exhibits pleochroism meaning that the intensity of the blue saturation changes as light enters it from different angles reflecting off different blue hues shown in the picture below, this is considered to be a rare feature of a gemstone and adds to its uniqueness.

Rough Grandidierite specimen exhibiting pleochroism as lights enters from 2 different angles.

However, crystallised Grandidierite has only been seen for the first time by mankind only less than 2 decades ago even though it was originally discovered in the year 1902, these crystallised transparent specimens of Grandidierite discovered in Sri lanka in the year 2004 possessed a lower fe and mg content which allowed it to be transparent and it is the purest form of Grandidierite the world has ever seen, however the largest gem quality piece that was extracted from this deposit weighed in at only 0.29 carats. The mineral was then to not be found again until a decade later in its biggest ever discovery of crystallised Grandidierite, this deposit was located near its original discovery location in cape Andrahomana, located near a town named Tranamaro, this deposit is believed to possibly be the only crystallised deposit of this mineral to ever be discovered due to the southern coast of the island of Madagascar being possibly the only area in the world which possesses the perfect amount of Fe (fe-mg) content for the mineral to form in its crystallised form, anything above or below affects the clarity of the stone dramatically explaining why the reason why the ratio of translucent to transparent material extracted in the deposit being 1:10000.


Unlike the other worlds top 10 rarest gemstones such as Benitoite, Black opals and Jadietes which possesses a hardness of 6 or 6.5, Grandidierite is considered to be a fairly durable stone, with the hardness of 7.5 on the Moh scale, Grandidierite would be a perfect match to be used as a center stone in jewelry due to its high resistance to almost every type of scratching it may experience.

Grandidierite is also a completely natural and unenhanced gemstone, with 90% of the gemstones in the market being enhanced using the processes such as heating at an extremely high temperature to improve its colour, or oiling the gemstones to improve its clarity and colour and changing the gems from its natural state, these methods nowadays are so advanced it is almost undetectable to an untrained eye, therefore the fact that Grandidierite is 100% in its natural state, it brings an instant peace of mind to any rare gems lover or collector.

In the year 2015, Forbes magazine valued Grandidierite at 20000 dollars a carat exceeding prices of other worlds most expensive gemstones such as Alexandrites and Benitoite, and the reason for this is explained by the rarity of the crystallised form of Grandidierite, with 800 kilograms of rough Grandidierite being extracted from the Tranamaro deposit only 60 grams of the entire deposit found are transparent stones which are extremely small rough crystals that when faceted, over 50% of the weight is lost meaning that it could be said that a perfectly clean piece of Grandidierite weighing over 2-2.5 carats is nearly non existent. The majority of Grandidierite rough extracted also have inclusions of other gemstones such as Zircon and Monazites which affects its purity and colour of the stone meaning even the translucent material itself is not pure and a clean piece of the translucent material is still extremely valuable.