Mother nature has gifted us with an incredible array of gemstone minerals, each with its own set of unique characteristics and extraordinary beauty. While many are familiar with popular gemstones such as diamonds, rubies, and sapphires, our planet also houses a fascinating collection of lesser-known, unusual gemstones.
In this blog post, we will delve into the world of these rare minerals, exploring their unique features, the locations where they are found, and the qualities they exhibit. Prepare to be mesmerized as we uncover the rare, the exotic, and the truly extraordinary hidden treasures of the Earth. From captivating colours to enigmatic formations, these remarkable gems will intrigue and delight collectors and enthusiasts alike.
1. Csarite (Diaspore)
Csarite, also known as Diaspore, is a rare colour-change gemstone that exhibits different colours depending on the lighting conditions. This chameleon-like quality makes it a fascinating and unusual gemstone.
Where it's found: Csarite has only ever been found in the Anatolian Mountains of Turkey, making it a rather exclusive and rare find.
Qualities: Csarite exhibits a colour change from a kiwi-green hue in daylight to a raspberry-pink shade under incandescent lighting. Some specimens may also display a champagne colour in different lighting conditions. The gemstone is transparent with a vitreous lustre and has a hardness of 6.5-7 on the Mohs Scale.
Figure 1: A Csarite Ring
2. Painite
Once considered the rarest gemstone on Earth, painite was first discovered in 1951 by British mineralogist Arthur C. D. Pain, who misidentified it as a ruby. For many years, only a few specimens were known to exist. Painite is so rare that it was once more valuable than diamonds. Due to its scarcity, a single carat of this stone can cost between $50,000 and $60,000.
Where it's found: Painite is currently only found around the Mogok Valley in Myanmar, which is also home to some of the world’s most exquisite Rubies.
Qualities: Painite is a hexagonal crystal that ranges in colour from reddish-brown to deep red or orange. Some specimens exhibit pleochroism – an optical phenomenon where the stone’s colour changes depending on its viewing angle.
Figure 2: A Painite Crystal
3. Pallasite Peridot
Perhaps the most curious of gemstones on this list, Pallasite peridot is a rare extra-terrestrial gemstone found within pallasite meteorites. This interplanetary mineral is an olivine crystal that has been encapsulated in a meteorite's metal matrix, making it a unique blend of gemstone and meteorite material.
Where it's found: Pallasite peridot is found in pallasite meteorites, which have been discovered in various locations worldwide, including Argentina, Russia, and the United States.
Qualities: Pallasite peridot exhibits a vibrant green colour and is transparent with a vitreous lustre. The presence of metal inclusions and the gemstone's extra-terrestrial origin make it truly distinctive.
Figure 3: Gem-quality Pallasite Peridots (Source: GIA)
4. Poudretteite
Discovered in 1965 in a quarry in Mont St. Hilaire, Quebec, poudretteite was named after the Poudrette family, who operated the quarry. This gemstone remained a rarity until 2000, when larger, gem-quality crystals were discovered in Myanmar. This particular mineral has a barely-detectable radioactivity, making it extremely difficult to locate.
Where it's found: So far, Poudretteite has been found only in minute traces in Canada and some relatively larger pieces have been discovered in Myanmar.
Qualities: Poudretteite is a transparent gemstone with a vitreous lustre. It typically exhibits a pale pink to lavender colour, although some specimens can be colourless or exhibit a more intense pink hue.
Figure 4: A rough Poudretteite mineral
5. Grandidierite
Named after French explorer Alfred Grandidier, who studied Madagascar's natural history, grandidierite is an extremely rare gemstone. Since its discovery in 1902, only a few gem-quality specimens have been found. A distinguishing feature of this mineral is that is displays a strong trichroic pleochroism. This means that the mineral can show 3 different colours depending on the viewing angle – dark blue-green, colourless, or dark green.
Where it's found: For many years, Cap Andrahomana in southern Madagascar, was the only source of gem-quality grandidierite. New sources include Sri Lanka, Algeria, and the USA.
Qualities: Grandidierite is a relatively hard mineral, rating in at 7.5 on the Mohs Scale. The gemstone has a vitreous to pearly lustre and is transparent to translucent.
Figure 5: A gem-quality Grandidierite
6. Benitoite
First discovered in 1907, benitoite is a rare gemstone that exhibits an exceptional blue colour and strong dispersion, giving it a dazzling fire similar to diamonds. Benitoite is also the official state gemstone of California.
Where it's found: Gem-quality Benitoite is found almost exclusively in the Diablo Range in San Benito County, California.
Qualities: Benitoite exhibits a vivid blue colour, often compared to sapphires, but can also be found in shades of purple or, rarely, colourless. The gemstone is transparent with a vitreous lustre and has a unique crystal structure that forms triangular or tabular crystals.
Figure 6: Benitoite crystals within a rough mineral
7. Taaffeite
Taaffeite was first discovered by chance in 1945 when gemmologist Richard Taaffe purchased a spinel that turned out to be a new gemstone – never formally recognized or discovered before. This incredibly rare gemstone is often discovered accidentally among other gemstones, as it can be mistaken for spinel or sapphire.
Where it's found: Gem-quality taaffeite has only been found in Sri Lanka, Tanzania, and Myanmar, so far.
Qualities: Taaffeite exhibits a range of colours, including pale pink, lilac, lavender, and red. The gemstone is transparent with a vitreous lustre.
Figure 7: A Taaffeite gemstone
Our planet is home to a vast array of unusual and breath-taking gemstone minerals. From the fiery red beryl to the extra-terrestrial Pallasite peridot, these rare gemstones capture the imagination and showcase the remarkable diversity of Earth's geological wonders. Whether you're an avid collector, a jewellery lover, or simply curious about the wonders of the natural world, these unusual gemstones offer a glimpse into the amazing variety and range of colours, shapes, and textures that can be found within the earth's crust.
