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Three extraordinary new gem minerals, each unique in their size and clarity, have been put on public display in The Vault, which can be visited in the Museum's mineral gallery.
The minerals, Tanzanite, Morganite and Rhodochrosite, are currently on loan to the museum for one year. Each one is richly coloured, great in size and scientifically significant.
They can be seen alongside a huge range of other extraordinary specimens, including one of the most comprehensive collections of naturally coloured diamonds in the world and rocks dating back to the beginning of the solar system.
Known more widely as a gem with pale, milky-pink banding, on rare occasions rhodochrosite can also form beautiful deep red crystals as seen with this specimen. This is a manganese carbonate mineral, with the name 'rhodochrosite' derived from the Greek for 'rose-coloured'.
This particular specimen was discovered in the Sweet Home mine, Colorado. Originally opened in 1873 to explore for silver, occasionally the miners would come across these stunning red crystals. While the mine eventually closed in 1967 after the silver deposits were exhausted to an extent it was no longer profitable, the mine had already built a reputation for the incredible rhodochrosite crystals found here. In 1991 the mine was reopened specifically to mine for these gem minerals, with this specimen being discovered just a year later in 1992 in a pocket which was named the Good Luck Pocket.
First discovered in Madagascar in 1910, morganite is a variety of the mineral Beryl. Pure Beryl is colourless, and it is only when this mineral contains impurities that it takes on characteristic hues. The pink colour of morganite is attributed to Manganese ions, but other varieties of Beryl include the blue aquamarine and the green-coloured emeralds.
Beryl is interesting as it contains the rare element beryllium, and is in fact the main ore for this element which is used in the aerospace industry. This mineral is commonly found within a rock known as pegmatite, which are well-known for containing gem minerals due to the rock's formation process which concentrates rare elements in quantities sufficient for gem minerals such as Beryl to grow.
This particular specimen is from Urucum mine in Brazil and is 11 centimetres wide, clearly showing off its hexagonal symmetry. But in some cases, crystals of Beryl can reach an extraordinary 18 metres long, although these enormous crystals are not of the quality needed for gems.
This violet-blue gem mineral is a variety of the mineral zoisite. Only found in gem quality in the Merelani Hills of Tanzania, tanzanite is a relative newcomer on the gem scene having only been discovered in 1967. This large specimen has been saved from cutting into gemstones, and is made up of two crystals attached to each other.
This mineral is well known for an optical property in which the crystals appear different colours when viewed from different directions, known as pleochroism. The crystal appears blue from one side, violet from the other and reddish when viewed from the top. This is caused by light interacting differently with the internal atomic structure of the crystal as it travels through the specimen in each direction.
Visit the three new minerals, plus an amazing array of other gems, minerals and crystals displayed alongside them in The Vault, open daily in the minerals gallery.