Keep in mind that scratch tests for hardness should only be used as a last resort to identify rough, so don’t conduct this test on a finished gemstone. Grandidierites also have greater hardness.

Nevertheless, lazulites have somewhat higher refractive indices (RI) and specific gravity (SG). They also appear cabbed and, more rarely, faceted.

While trichroism can usually help distinguish grandidierites from other gems, lazulites can occur with blue-green colors and show colorless/blue/dark blue pleochroism. That means they can show three different colors depending on the viewing angle: dark blue-green, colorless (sometimes very light yellow), or dark green. Grandidierites display strong trichroic pleochroism. Recent discoveries of transparent material in Sri Lanka (around 2000) and a new deposit in Madagascar (2014) have resulted in beautiful, faceted gemstones. Cabochons cut from this material look very attractive and may even appear jade-like. Since its discovery in 1902, most gem-quality grandidierite has been translucent. Of course, its scarcity has also made this a relatively little-known gemstone. However, it also has perfect and good cleavage in two directions, which makes it challenging to cut. Grandidierite has a hardness of 7.5, which makes it very resistant to scratching and ideal for jewelry use. Does Grandidierite Make a Good Jewelry Stone? Grandidierites in a cluster of crystals, from Cap Andrahomana, Ranopiso Department, Anosy (Fort Dauphin) Region, Tuloar Province, Madagascar. Strong: dark blue-green/colorless/ dark green.Ī = 1.583-1.602 β = 1.618-1.636 γ = 1.622-1.639. Biaxial (-), 2 V = 30°.Īfter Alfred Grandidier, a French explorer who described the natural history and geography of Madagascar.Ĭrystals (chlorapatite, monazite, zircon), two phase inclusions (vapor/liquid), needle-like channels, parallel growth planes. Gem material is translucent to transparent. Crystals elongated and not well formed massive. Faceted pieces are very rare, but recent discoveries of transparent material may bring more to the market. Translucent material is sometimes cut into cabochons.

A rather rare mineral, lovely blue-green grandidierite is seldom seen in gem or jewelry collections.

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