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Contents 1 Meet the family 2 Garnet names 3 Garnets in history 4 Gemological properties 5 Online G&G articles on garnet

Meet the family

Admired by mankind as long as history can take us back and available in many colors, garnets have been an important gem material throughout times. Both historical and archaeological research dates the use of garnets as a gem material back to the earliest civilisations on this planet.

The family has possibly gained its name after the red varieties which resemble the seeds of a pomegranate in color. The term garnet now stands for a whole family of minerals that crystallizes in the cubic system and shares the same chemical blueprint. The elements used to fill that blueprint make a gem garnet belong to one or more of the following family members:

• Pyrope: Mg₃Al₂(SO₄)₃ (magnesium aluminum silicate)
• Almandine: Fe₃Al₂(SiO₄)₃ (iron aluminum silicate)
• Spessartine: Mn₃Al₂ (SiO₄)₃ (manganese aluminium silicate)
• Grossular: Ca₃Al₂(SiO₄)₃ (calcium aluminum silicate)
• Hydrogrossular: Ca₃Al₂(SiO₄)_3-x(OH)_4x (calcium aluminum silicate with hydroxide)
• Andradite: Ca₃Fe₂(SiO₄)₃ (calcium iron silicate)

Garnet names

It would have been easy if nature presented us with pure family members. That, unfortunately for those trying to classify garnets, but luckily for you isn't the case. The family members that are listed above represent end members within the garnet group. In other words: their composition is an ideal, theoretical one. In reality all the garnets we use as gem materials are a mix of two or more end members in various ratios. Some of the magnesium which makes a pyrope a pyrope can be replaced by iron, or some of the iron that makes an almandine an almandine is replaced by manganese. In gemology this 'mixing of end members' is called isomorphous replacement. The composition of a garnet determines certain measurable characteristics of the stone such as refractive index and specific gravity. It can also influence the color of the stone and that is where you get lucky: garnets come in many colors and shades. The confusion which occurs from these mixed garnets together with marketing strategies have caused an array of trade names to be invented for various garnets. While it is scientifically correct to call the the green garnet found in Kenya a green grossular, you will never encounter it under any other name than Tsavorite. It just sells better that way. Some names are relatively new and are still being contested, others have been in use so long that they have gotten a firm grounding in literature and have been adopted by gemologists. It is important to remember that at the end of the day all garnets are a mix of two or more of the end members mentioned above.

Garnet names
Rhodolite	Anthill
Malaya	Hessonite
Tsavorite	Demantoid
Mandarin	Topazolite
Mali	Melanite

Below follows a diagram of trade names placed into context by their actual composition put together by dr. W. Wm. Hanneman:

Garnets in history

Garnets have been used wherever they occur for as long as mankind can remember. From predynastic Egypt to the discovery and hype of Fanta orange garnets in Tanzania in 2007, garnets have never ceased to capture our attention. The Roman writer Pliny mentions gemstones called carbuncles, some of which are thought to be garnets. The red family member almandine was a very popular gemstone with the Germanic tribes which inhabited northern Europe during Roman times. They were used for cloisonné inlay work of which the items found at Sutton Hoo are a great example.

In Victorian times garnets were extremely fashionable; rose cut garnets from the Czech Republic covered entire jewelry items. These garnets are better known as Bohemian garnets after the area they were mined: Bohemia.

In 1853 andradite was found in the Ural Mountains in Russia. This bright green garnet was named demantoid in 1878 and became a hot gemstone in 'turn of the century' jewelry. In the last quarter of the 20th century various garnet varieties have been found in Africa which enjoy a great popularity to this day.

Gemological properties

Gemological information for garnet
Color	all colors
Crystal Structure	Cubic
Refractive Index	1.74-1.89
Durability	Good
Hardness	6.6-7.5
Treatments	Usually not treated
Country of origin	Worldwide
Garnet care
Ultrasonic cleaning	Safe
Steam cleaning	Safe
Warm soapy water	Safe
Chemical attack	Avoid
Light sensitivity	Stable
Heat sensitivity	Stable

Online G&G articles on garnet

• July-Aug. 1934, Unusual Garnets, p. 125, 2pp.
• Summer 1945, Absorption Spectra of Pyrope Garnet, by Anderson, p. 232, 2pp.
  • Fall 1945, p. 257, 2pp. #3: Spring 1946, p. 301, 3pp.
• Summer 1947, Distinction between garnet and corundum, p. 435, 1p.
• Fall 1947, The Garnet. Past and Present, p. 465, 3pp.
• Spring 1948, Pyrandine, A New Name For An Old Garnet, by Anderson, p. 27, 1p.
• Winter 1950, Garnet produced from Madagascar, p. 378, 2pp.
• Summer 1953, Demantoid, by Ehrmann, p. 317, 1p.
• Summer 1954, Third find of rhodolite garnet; discovered in Greenland by John Sinkankas, p. 63, 1p.
• Fall 1960, A 19.65 ct. hessonite garnet (showing absorption spectrum), p. 72, 1p.
• Fall 1960, Cat's-eye demantoid, p. 92, 1p.
• Fall 1962, A ruby red 16 ct. chrome pyrope (showing absorption spectrum), p. 339, 1p.
• Spring 1963, Pink Grossularite Garnet, p. 23, 2pp.
• Summer 1963, Massive grossularite from S. Africa, by Webster, p. 35, 4pp.
• Summer 1966, Hydrogrossularite garnet from the Transvaal, p. 49, 9pp.
• Fall 1966, p. 74, 4pp.
  • Winter 1966, A 17 ct. faceted uvarovite garnet (showing absorption spectrum), p. 113, 2pp.
• Spring 1968, A ruby red 4.27 ct. chrome pyrope, p. 279, 1p.
• Winter 1968, Transparent green grossularite, p. 375, 1p.
• Spring 1969, Tanzanian garnets, p. 15, 2pp.
• Summer 1969, Emerald-green grossularite garnet, p. 58, 1p.
• Summer 1969, A 2-phase inclusion in garnet (first seen), p. 67, 2pp.
• Winter 1969, A fine 6 ct. demantoid garnet showing horsetail inclusions, p. 121, 2pp.
• Spring 1970, New transparent green grossularite inclusions, p. 151, 2pp.
• Spring 1970, Alexandrite-like garnet from Tanzania, p. 162, 1p.
• Summer 1970, A rare Alexandrite Garnet from Tanzania, p. 174, 4pp.
• Summer 1970, Spessartite garnet inclusions, p. 189, 1p.
• Summer 1970, Spessartite absorption spectrum, p. 197, 2pp.
• Summer 1970, Grossularite garnet inclusions, p. 196, 2pp.
• Fall 1970, Testing demantoid with ultra-violet light, p. 226, 2pp.
• Fall 1970, New transparent colorless grossularite from Tanzania, p. 227, 3pp.
• Fall 1970, Alexandrite garnet from Norway, p. 229, 1p.
• Fall 1971, A massive hydrogrossular garnet cut in cabochon (one end pink, the other end green) (showing absorption spectrum), p. 354, 3pp.
• Summer 1972, Two unusual rhodolite property variations, p. 40, 1p.
• Spring 1973, A typical demantoid inclusion, p. 150, 1p.
• Summer 1974, Green grossularite garnets, "tsavorites" on the Kenya-Tanzania border, p. 290, 6pp.
• Summer 1974, Composition of "tsavorites" from Kenya and Tanzania, by Switzer, p. 296, 2pp.
• Fall 1974, Jewelry repair involving garnet and glass doublets, dangerous, p. 344, 2pp.
• Fall 1974, Some unusual inclusions in hessonite and rhodolite, p. 349, 2pp.
• Winter 1978, Blue to Red Colour Changing Garnet from East Africa, p. 122, 2pp.
• Winter 1978, Demantoid garnet from Korea; Alexandrite garnet from East Africa, p. 123, 3pp.
• Summer 1979, Colorless and Green Grossularite from Tanzania, by Pieter Muije, p. 162, 12pp.
• Fall 1979, Unusual Gem Garnets of East Africa, p. 218, 2pp.