Tsavorite

Last updated
Tsavorite
Graphite-Grossular-Strontiumapatite-d06-195a.jpg
Tsavorite garnet on real matrix of silvery black graphite and a minor blue apatite
General
Category Nesosilicate
Formula
(repeating unit)		Ca3Al2Si3O12
Crystal system Cubic
Identification
ColorLight to deep green
Mohs scale hardness7.0–7.5 [1]
Specific gravity 3.60–3.68 [1]
Optical propertiesSingle refractive
Refractive index 1.740 [1]
Dispersion 0.028 [1]

Tsavorite or tsavolite is a variety of the garnet group species grossular, a calcium-aluminium garnet with the formula Ca 3 Al 2 Si 3 O 12. [2] Trace amounts of vanadium or chromium provide the green color.

In 1967, British gem prospector and geologist Campbell R. Bridges discovered a deposit of green grossular in the mountains of Simanjiro District of Manyara Region of north-east Tanzania [3] in a place called Lemshuko, 15 km (9.3 mi) away from Komolo, the first village. The specimens he found were of very intense color and of high transparency. The find interested the gem trade, and attempts were made to export the stones, but the Tanzanian government did not provide permits.

Believing that the deposit was a part of a larger geological structure extending possibly into Kenya, Bridges began prospecting in that nation. He was successful a second time in 1971, when he found the mineral variety there, and was granted a permit to mine the deposit. The gemstone was known only to mineral specialists until 1974, when Tiffany and Co launched a marketing campaign which brought broader recognition of the stone. [3]

Bridges was murdered in 2009 when a mob attacked him and his son on their property in Tsavo East National Park. It is believed that the attack was connected to a three-year dispute over access and control of Bridges' gemstone mines. [4] [5]

The name tsavorite was proposed by Tiffany and Co president Henry Platt in honor of Tsavo East National Park in Kenya. [3] Apart from this source and the first discovered locality in Manyara, Tanzania, it is also found in Toliara (Tuléar) Province, Madagascar. Small deposits of gem grade material have been found in Pakistan and Queen Maud Land, Antarctica. No other occurrences of gem material have yet been discovered. [6]

Rare in gem-quality over several carats (1 carat = 200 mg), tsavorite has been found in larger sizes. In late 2006, a 925-carat (185.0 g) crystal was discovered. It yielded an oval mixed-cut 325 carat (65 g) stone, one of the largest, if not the largest, faceted tsavorites in the world. A crystal that yielded a 120.68-carat (24.136 g) oval mixed-cut gem was also uncovered in early 2006. [7] The Lion of Merelani is a square cushion cut tsavorite that weighs 116.76 carats and has 177 facets. It is on display at the Smithsonian Institution.

Tsavorite formed in a Neoproterozoic metamorphic event which involved extensive folding and refolding of rock. This resulted in a wide range of inclusions forming within most Tsavorite crystals. These inclusions are strong identifying features in Tsavorite. [8]

Related Research Articles

<span class="mw-page-title-main">Emerald</span> Green gemstone, a beryl variety

Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium or sometimes vanadium. Beryl has a hardness of 7.5–8 on the Mohs scale. Most emeralds have lots of material trapped inside during the gem's formation, so their toughness (resistance to breakage) is classified as generally poor. Emerald is a cyclosilicate.

<span class="mw-page-title-main">Gemstone</span> Piece of mineral crystal used to make jewelry

A gemstone is a piece of mineral crystal which, when cut or polished, is used to make jewelry or other adornments. However, certain rocks and occasionally organic materials that are not minerals are also used for jewelry and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their luster or other physical properties that have aesthetic value. Rarity and notoriety are other characteristics that lend value to gemstones.

<span class="mw-page-title-main">Spinel</span> Mineral or gemstone

Spinel is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula MgAl
2O
4 in the cubic crystal system. Its name comes from the Latin word spinella, a diminutive form of spine, in reference to its pointed crystals.

<span class="mw-page-title-main">Sapphire</span> Gem variety of corundum

Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al2O3) with trace amounts of elements such as iron, titanium, cobalt, lead, chromium, vanadium, magnesium, boron, and silicon. The name sapphire is derived via the Latin sapphirus from the Greek sappheiros (σάπφειρος), which referred to lapis lazuli. It is typically blue, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors. Red corundum stones also occur, but are called rubies rather than sapphires. Pink-colored corundum may be classified either as ruby or sapphire depending on locale. Commonly, natural sapphires are cut and polished into gemstones and worn in jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of special-purpose solid-state electronics such as integrated circuits and GaN-based blue LEDs. Sapphire is the birthstone for September and the gem of the 45th anniversary. A sapphire jubilee occurs after 65 years.

<span class="mw-page-title-main">Garnet</span> Mineral, semi-precious stone

Garnets are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives.

<span class="mw-page-title-main">Ruby</span> Variety of corundum, mineral, gemstone

A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum. Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapphires. Ruby is one of the traditional cardinal gems, alongside amethyst, sapphire, emerald, and diamond. The word ruby comes from ruber, Latin for red. The color of a ruby is due to the element chromium.

<span class="mw-page-title-main">Chrysoberyl</span> Mineral or gemstone of beryllium aluminate

The mineral or gemstone chrysoberyl is an aluminate of beryllium with the formula BeAl2O4. The name chrysoberyl is derived from the Greek words χρυσός chrysos and βήρυλλος beryllos, meaning "a gold-white spar". Despite the similarity of their names, chrysoberyl and beryl are two completely different gemstones, although they both contain beryllium. Chrysoberyl is the third-hardest frequently encountered natural gemstone and lies at 8.5 on the Mohs scale of mineral hardness, between corundum (9) and topaz (8).

Diamond cutting is the practice of shaping a diamond from a rough stone into a faceted gem. Cutting diamonds requires specialized knowledge, tools, equipment, and techniques because of its extreme difficulty.

<span class="mw-page-title-main">Tanzanite</span> Blue to purple variety of the mineral zoisite

Tanzanite is the blue and violet variety of the mineral zoisite, caused by small amounts of vanadium. Tanzanite belongs to the epidote mineral group. Tanzanite is only found in Simanjiro District of Manyara Region in Tanzania, in a very small mining area approximately 7 km (4.3 mi) long and 2 km (1.2 mi) wide near the Mererani Hills.

<span class="mw-page-title-main">Cuprite</span>

Cuprite is an oxide mineral composed of copper(I) oxide Cu2O, and is a minor ore of copper.

<span class="mw-page-title-main">Demantoid</span> Green gemstone variety of the mineral andradite

Demantoid is the green gemstone variety of the mineral andradite, a member of the garnet group of minerals. Andradite is a calcium- and iron-rich garnet. The chemical formula is Ca3Fe2(SiO4)3 with chromium substitution as the cause of the demantoid green color. Ferric iron is the cause of the yellow in the stone.

<span class="mw-page-title-main">Diamond simulant</span> Diamond-like object which is not a diamond

A diamond simulant, diamond imitation or imitation diamond is an object or material with gemological characteristics similar to those of a diamond. Simulants are distinct from synthetic diamonds, which are actual diamonds exhibiting the same material properties as natural diamonds. Enhanced diamonds are also excluded from this definition. A diamond simulant may be artificial, natural, or in some cases a combination thereof. While their material properties depart markedly from those of diamond, simulants have certain desired characteristics—such as dispersion and hardness—which lend themselves to imitation. Trained gemologists with appropriate equipment are able to distinguish natural and synthetic diamonds from all diamond simulants, primarily by visual inspection.

<span class="mw-page-title-main">Spessartine</span> Nesosilicate, manganese aluminium garnet species

Spessartine is a nesosilicate, manganese aluminium garnet species, Mn2+3Al2(SiO4)3. This mineral is sometimes mistakenly referred to as spessartite.

<span class="mw-page-title-main">Grossular</span> Garnet, nesosilicate mineral

Grossular is a calcium-aluminium species of the garnet group of minerals. It has the chemical formula of Ca3Al2(SiO4)3 but the calcium may, in part, be replaced by ferrous iron and the aluminium by ferric iron. The name grossular is derived from the botanical name for the gooseberry, grossularia, in reference to the green garnet of this composition that is found in Siberia. Other shades include cinnamon brown (cinnamon stone variety), red, and yellow. Grossular is a gemstone.

<span class="mw-page-title-main">Andradite</span> Nesosilicate mineral species of garnet

Andradite is a mineral species of the garnet group. It is a nesosilicate, with formula Ca3Fe2Si3O12.

<span class="mw-page-title-main">Rhodolite</span> Rose-colored gemstone of the garnet group

Rhodolite is a varietal name for rose-pink to red mineral pyrope, a species in the garnet group. It was first described from Cowee Valley, Macon County, North Carolina. The name is derived from the Greek "rhodon" for "rose-like", in common with other pink mineral types. This coloration, and the commonly inclusion-free nature of garnet from this locality, has led to rhodolite being used as a gemstone. Rhodolite like other varietal names is not officially recognized as a mineralogical term, but rather used as an accepted trade name.

<span class="mw-page-title-main">Diamond (gemstone)</span> Gemstone

Diamond is one of the best-known and most sought-after gemstones. They have been used as decorative items since ancient times.

<span class="mw-page-title-main">Jeremejevite</span>

Jeremejevite is an aluminium borate mineral with variable fluoride and hydroxide ions. Its chemical formula is Al6B5O15(F,OH)3. It is considered as one of the rarest, thus one of the most expensive stones. For nearly a century, it was considered as one of the rarest gemstones in the world.

Campbell R. Bridges was a Scottish-born Kenyan gemologist.

The Lion of Merelani is a tsavorite gemstone from Tanzania that is in the collection of the National Museum of Natural History of the Smithsonian Institution in Washington, DC. The gemstone weighs 116.76 carats, has 177 facets, and is an intense green color. It was donated in the memory of Campbell R. Bridges, the gemologist who discovered tsavorite, who was murdered in 2009. It is the largest known tsavorite gemstone and the largest fine gemstone ever to be cut and polished in the United States.

References

  1. 1 2 3 4 Bancroft, Peter (4 September 2002). "Tsavorite". Pala International. Archived from the original on 29 May 2023. Retrieved 16 September 2023.
  2. ↑ "Tsavorite". Mindat.org.
  3. 1 2 3 "Tsavorite". International Colored Gemstone Association. Archived from the original on 2008-06-10. Retrieved 16 September 2023.
  4. ↑ "Mob kills UK gems expert in Kenya". BBC News. 13 August 2009. Archived from the original on 7 September 2023. Retrieved 16 September 2023.
  5. ↑ Pflanz, Mike (12 August 2009). "Machete mob murders British gemstone miner in Kenya". The Telegraph. Nairobi. Archived from the original on 7 September 2023. Retrieved 16 September 2023.
  6. ↑ Arem, Joel E.; Clark, Donald. "Tsavorite Garnet Value, Price, and Jewelry Information". International Gem Society. Archived from the original on 20 July 2023. Retrieved 16 September 2023.
  7. ↑ Weinberg, David (7 January 2007). "Giant size top color clean tsavorite discovered in East Africa". Multicolour Gems Ltd. Archived from the original on 30 May 2023. Retrieved 16 September 2023.
  8. ↑ Zagoritis, Antony. "Common and Uncommon Inclusions Found in Tsavorite". The Rare Gemstone Company. Archived from the original on 9 June 2023. Retrieved 16 September 2023.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.