Zoisite is the mineral of some very diverse gem materials, one being the extremely popular tanzanite.
The name Zoisite comes from the Slovenian scientist Ziga Zois who first identified the material in the Sau-Alp mountains in Austria, in 1805. It was originally called Saualpite.
Zoisite is a mineral that includes several gem varieties but always occurs as prismatic crystals. It is diverse in colour, ranging from pink to yellow, green and blue to brown. The most common colours are blue and violet.
It is quite difficult to work with due to its huge difference in hardness. The higher the transparency of this gem, the higher the value.
The color of Zoisite is variable but well known as green, blue to violet and pink to reddish in color, Also grey, white or brown. It has a very vitreous lustre and its crystals are transparent to translucent.
Hardness: 6.5
Inclusions: Finer print and healing cracks
Localities: Tanzania (specifically Merelani)
Emeralds are the most valuable member of the beryl family and owe their distinctive green colour to traces of chromium, found present during crystal growth. Most Emeralds have visible inclusions that permeate the stone, affectionately called the jardin.
Emeralds have been mined in Egypt since around 1500 BC where there were a group of mines near the Red Sea, the Cleopatra's mines. Cleopatra is said to have bestowed visiting dignitaries with emeralds engraved with her portrait.
Hardness: 7.5
Inclusions: Emerald can contain three-phase inclusion. A micro-pocket of liquid with a trapped gas bubble & small solid crystal due to growing .
Localities: The finest and rarest Emeralds can be found in Columbia with a distinctive vibrant green. Other sources Brazil, Zambia, Austria, India, China Australia, South Africa, Egypt, the USA, Norway, Pakistan and Zimbabwe.
Birthstone: May
Mythology: In Egyptian times emeralds represented rebirth, fertility and immortality. More recently they are believe to strengthen memory, provide mental clarity and ease a stressed state.
Demantoid is the most valuable garnet. It is an emerald green colour due to the presence of chromium and the high refractive index, which in other garnet gems can be masked by the depth of their colour, renders these remarkable stones very brilliant. This, matched with their high dispersion, means these gems are full of life with flash of colour catching your eye as the light moves through the gem. They resemble diamonds in this respect, hence the name Demantoid.
Hardness: 6.5 to 7
Inclusions: Demantoids often have diagnostic “horsetail” inclusions which are made up of radiating fibrous golden threads around a small crystal. Rather than hindering the beauty of the stone these inclusions are sought after and a particularly well formed "horsetail" can increase the price as collectors vie to add this to their treasure trove.
Localities: Russia (Ural Mountains), Namibia, Iran and Italy.
The colour of Kyanite can vary from blue, white, green, yellow, pink to almost black. Crystals are often found in blades with darker bands of colour towards the center.
When cut they can give a bright vitreous lustre but the transparent blue gems often display distinctive colour banding. Since they can be soft they are often found as beads and cabochons.
Hardness: Between 5 and 7
Localities: Gem quality crystals are found in Burma, Brazil, Mozambique, Madagascar and Kenya.
Mythology: Some say that Kyanite is good for communication and speaking the truth making it useful for performers and public speakers.
For centuries Jade was thought to be a single gemstone, but in 1836 two types were recognised; Jadeite and Nephrite.
The colour of jadeite is typically green but can be white, grey, lavender and when stained by iron oxides, brown or yellow. The highest quality is semitransparent and a distinctive vivid green. This is also known as “Imperial Jade”.
Nephrite jade can vary in colour from dark green to a pure white which is referred to as “mutton fat jade”. Its colour is less vibrant than jadeite and is often mottled.
Jadeite is slightly harder than nephrite and was the favoured material for the fashioning of implements employed by primitive man.
Hardness: Jadeite 6.5 to & and Nephrite 6.0 to 6.5
Inclusions: Jade is a microcrystalline material which means that it has no inclusions however if the material is dyed you will notice that the colour is concentrated in the cracks.
Treatments: “A Jade” means that the Jadeite is untreated while “B Jade” means that the material has been bleached or impregnated with synthetic resins. Finally “C Jade” means that a dye has been use to improve the colour from colourless to either green or lavender.
Localities: Burma, Guatemala, Japan, Russia and USA.
Mythology: Jade has always been highly regarded by the Chinese and was often buried with Kings to protect their body from decay. Jade is still thought of as protective hence the tradition of giving and wearing jade bangles in China.
Aquamarine translates to “water of the sea” and they are the light green, greenish blue to blue variety of beryl. The colour is due to the iron content.
Today the most valued colours are a rich, saturated blue described as “Santa Maria”, referencing the exquisite Aquas extracted from the famous mine Santa Maria de Itabira in Brazil.
Aquamarines can be found in alluvial deposits and those which occur in pegmatites can grow to a significant size. The largest ever faceted Aquamarine started as a 2ft long crystal and ended as the Dom Pedro Aquamarine which is 10,363 carats and stands 35cm tall. This natural beauty is proudly on display at the Smithsonian National Museum of Natural History in America.
A lot of aquamarines are heat treated to enhance their colour by removing any green hue and leaving pure blue.
Hardness: 7.5
Inclusions: Whilst many gem quality Aquamarines are clean, many have long two-phase tube inclusions which run parallel to the length of the crystal, evocative of falling rain.
Localities: Brazil, Madagascar, Burma, Russia, Afghanistan, Pakistan, Sri Lanka, Zambia, Kenya, Zimbabwe, Namibia and Nigeria.
Birthstone: March
Mythicism: Due to its association with the sea, Aquamarine was traditionally a sacred gem for sailors. It is believed that the Greeks wore amulets made of Aquamarine engraved with Poseidon, The Lord of the Sea, to help protect them on voyages.
As some of the most abundant phosphate minerals on earth, apatites are often confused with other minerals hence its name originates from the the Greek word apate, meaning, “to deceive”.
Despite being relatively soft, apatite can make beautiful gemstones or beads. It is often set into more protective mountings that capture light yet safely display its beauty.
Whilst apatite comes in white, yellow, green, blue and violet, the gem quality stones are most often yellow or blue. Spanish apatite is commonly called “asparagus stone”, due to its yellowish green colour. Being a pleochroic gemstone, blue apatite’s body colour can change from green-blue to blue depending on which way viewed.
Apatite is the most widely used method for estimating the amount of water in lunar rocks. In 2010, deposits of apatite were found in the surface of the moon, which astronomers declared to be evidence of water deposits in the ancient past.
Hardness: 5
Inclusions: Anything over 5 carats is not usually eye clean.
Localities: Burma, Spain, Brazil, Canada, USA and Sri Lanka.
Mythology: Mystics believe that Apatite can stimulate the thoughts and ideas of the wearer. It is said to help you maintain focus, concentrate effectively, think clearly, and communicate better.
Peridot is the gem variety of the mineral Olivine. It is one of the few gemstones which come in one colour only. The rich, green colour with the slight tinge of gold is caused by very fine traces of iron. This colour is how it has gained the nickname, 'evening emerald' . Peridot cat's eyes and star peridot are particularly rare and precious.
You can often find peridot (but rarely gem-quality) within lava rocks but the rarest source of Peridot is extraterrestrial since it has been discovered within meteorites.
Whilst having little brilliance and lustre it still possesses a subtle luxurious charm.
Hardness: 6.5 to 7
Inclusions: Due to internal stress cracks created around black chromite crystals, Peridots have a diagnostic inclusion which resembles waterlily leaves.
Localities: Egypt, China, Burma, Brazil and South Africa.
Birthstone: August
Mythology: In Hawaii, Peridot symbolises the tears of Hele who is the goddess of fire and volcanoes. It is also the stone given to celebrate the 16th year of marriage.
Tsavorite is a transparent, green grossular garnet and has a particularly amazing brilliance. Its colour can vary from blue-green to yellowish-green depending on the amount of vanadium and/or chromium present.
Tsavorite was first discovered by Geologist Campbell Bridges in Tanzania in 1967 and then in Kenya in 1971. He, along with Henry Platt, the president of Tiffany & Co. at the time, decided to name the gem after the nearby nature reserve, the Tsavo National Park on the Kenya-Tanzania border.
Hardness: 7.5
Inclusions: Tsavorite has very few inclusions and is occasionally flawless.
Localities: Kenya, Tanzania, Zambia, Madagascar and Pakistan.
Mythology: It is believed to be a stone of wealth, as well as having restorative and freeing qualities.
This mineral rarely forms crystals but when they occur, it is as small, short, prismatic specimens. The colour is pale to sky blue to dark green.
Turquoise is a polycrystaline mineral which forms in igneous and sedimentary aluminum rich rocks that have been much altered by copper-rich seeping groundwater. The gem quality material occurs in nodules and seams often with veins of matrix running through and can be translucent to opaque. When polished it has a waxy or dull vitreous “porcelain” lustre.
The colour varies from a green, blue-green through to a pure and a rich sky blue evocative of a Robin’s egg. The highly sought after turquoise from Arizona is called Sleeping Beauty Turquoise and is largely free from veining.
Turquoise has been used for decoration all around the world for thousands of years from adorning the domes of Iranian palaces, to being used in Aztec icons and being buried with ancient Egyptian rulers.
Hardness: 5.5 to 6
Treatments: Turquoise can be stabilized with a resin or plastic if it is very porous to make the stone more durable and this is often hard to detect. You can also find reconstructed turquoise which is made up of powdered turquoise with resin which is far from the natural stone but can look very deceptive.
Localities: USA, Mexico, Egypt, China but some of the best still comes from Iran.
Birthstone: December
Mythology: It has long been thought to protect from evil and regards as a stone of the gods.
