November 2015 Newsletter: Exceptionally Rare Grandidierite from Madagascar

Grandidierite is a very rare mineral that was first discovered in southern Madagascar in the early 20th century. Since grandidierite is quite hard, high quality material has been cut as gemstones, making it one of the very rarest gems, in a class with varieties like benitoite, painite, taaffeite and jeremejevite. You will often see grandidierite included in lists of the 10 rarest gem varieties in the world.

Grandidierite was first found in 1902 by Alfred Lacroix, a French mineralogist, in a pegmatitic environment at Andrahomana in southeastern Madagascar. Lacroix named the mineral in honor of French explorer and naturalist Alfred Grandidier (1836–1912), the first authority on the natural history of Madagascar.

Since its initial discovery, samples of Grandidierite have been found in only a few locations around the world, including Malawi, Namibia and Sri Lanka. But the few gem quality specimens seem to come mainly from Madagascar.

Gemologically, grandidierite is a magnesium aluminum borosilicate. It has a hardness of 7 to 7.5 on the Mohs scale, similar to garnet; a density of 2.85 to 3.00, in the approximate range of tourmaline; and a refractive index of 1.590-1.623.

It forms in the orthorhombic crystal system. Grandidierite is typically bluish green in color and derives its distinctive color from traces of iron. Gemmy material is translucent to transparent. Fully transparent specimens are ultra rare. 

Since grandidierite is so rare, we took several specimens to GIA in Bangkok for verification. GIA confirmed the samples as natural untreated Grandidierite and they issued special reports (GIA Notable Letters) on several of the gems. The gems are described as "extremely rare" with "very high transparency," with Grandidierite characterized as "one of the rarest gemstones on Earth."

Several of our Grandidierites are over 2 carats, a very unusual size for these rare gems. The largest is 4.54 cts, which GIA described as follows: "Very fine, large gem-quality grandidierite with high degree of transparency and distinctive color like this 4.54 ct gemstone can be considered extremely scarce."

Based on our research on these rare gems, we believe our 4.54 ct gem is the largest faceted Grandidierite in the world. We have recently applied to the Guinness World Records organization to document this.

See our collection of Rare Grandidierite



Notable Gems from the AJS Collection

This month we feature new acquisitions to our collection, including a matching pair of 5 ct Paraiba Tourmalines and a 7.52 ct unheated Ceylon sapphire.

Click on a photo to see the details for the item.

10.96 ct Paraiba Tourmaline Matched Pair, Mozambique

10.96 ct Paraiba Tourmaline Matched Pair from Mozambique [SOLD]
An amazing matched pair of 5 carat Paraiba Tourmalines from Mozambique! These beautifully matched gems are a neon mint green that is remarkably vivid and bright. A rare treasure for the discerning collector. Certified by GemResearch Swisslab (GRS) as copper-bearing with no indication of thermal treatment. We are also offering the gems separately if you are interested in a single stone for a ring or pendant.

4.12 ct Tanzanite Ring in 18k White Gold

4.12 ct Tanzanite Ring in 18k White Gold  [SOLD]
A lovely 4.12 carat square Tanzanite set in 18k white gold with diamonds. The Tanzanite is a top violet blue, loupe clean, with excellent briliance. The elegant ring features a split shank with 40 diamonds with a total carat weight of 0.57 cts. A wonderful gift for someone special!

1.18 ct Mahenge Spinel, Tanzania

1.18 ct Spinel from Mahenge, Tanzania  [SOLD]

A small but truly exquisite pink-red Spinel from Mahenge, Tanzania. Top color, top clarity and top cutting ... this lovely round gem has incredible sparkle and the color really pops. This fine spinel will make a gorgeous ring set with a halo of diamonds. Guaranteed natural and untreated.

4.54 ct Grandidierite from Madagascar

4.54 ct Grandidierite from Madagascar [SOLD]

Grandidierite is very rare in gem quality, and transparent material is exceptionally rare, with most specimens under 1 carat. So this 4.54 ct Grandidierite is a very special piece for the rare gem collector. Certified by GIA with a Notable Letter that describes this gem as "extremely rare" with "very high transparency" with "an appealing bluish green coloration." The GIA letter concludes that "Very fine, large gem-quality grandidierite with high degree of transparency and distinctive color like this 4.54 ct gemstone can be considered extremely scarce."

See our collection of Rare Grandidierite

News from AJS and the Gems World

  • Sotheby’s to Auction the Queen Maria-José Ruby

    Sotheby's is to auction The Queen Maria-José Ruby Ring at their Geneva auction on November 11. The ruby and diamond ring was formerly part of the personal collection of the last Queen of Italy, Maria-José, who died in 2001. The ring, which was presented as a gift by the scholar Tammaro de Marinis on the occasion of Maria-José’s wedding to Crown Prince Umberto in 1930, is set with an 8.48 carat pigeon blood Burmese ruby. It has a pre-sale estimate of $6 to $9 million.

  • 75 ct Fancy Vivid Yellow Diamond sells for $3.6 million at Christie's

    The top lot in Christie's New York sale on October 20 was a 75.56 ct fancy vivid yellow cushion shape diamond. It sold for $3.6 million. "Fancy vivid" is the highest color grade for fancy colored diamonds.


Ask the Gem Experts

Each month we answer questions from our customers. We welcome your questions and you can submit a question from our contact page.

Do you sell a colour changing gem called Zultanite? HL, Singapore

Zultanite was one of the tradenames for the mineral known by the gemological name of Diaspore. It has also been sold under the name Csarite. Diaspore is a color change gem from Turkey with reasonably good hardness (6.5 to 7 on the Mohs scale). It's an attractive jewelry stone with a delicate color and a subtle color change from a kiwi-like green in daylight to a champagne color in incandescent light, and a light purplish-pink under low intensity lighting such as candelight.
See our collection of Color Change Diaspore.


Are the upcoming elections in Burma likely to change the American restrictions on importing Burmese ruby and jade? We've been waiting a long time to buy these gems. CT, USA

Free and fair democratic elections in Burma on November 8th would certainly help convince the US government that reform is real, particularly if there is a strong showing by Aung San Suu Kyi's NLD party. But the Americans have already lifted virtually all the sanctions against Burma, with the exception of the restrictions on ruby and jadeite. The main stumbling block is alleged widespread corruption in the lucrative jade trade by the military, senior figures from the former junta and individuals connected to the drug trade. So we are not expecting any change in US policy in the near term.


All the best in gems,

Arnold, Rung & Ron