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Introduction:
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The general name, garnet, refers to the most widely known, red to purplish red to reddish brown pyrope and almandite specimens of a broader mineral group. The name comes from an association with the pomegranite, a delightful fruit with small, red, gem-sized seeds. In all actuality, garnets range in color from light yellowish greens to vibrant greens and include a full spectrum of red shades. The differences are attributed to slightly differing mineral compositions and crystal structures within the group. Although the public is most familiar with the pyrope and almandite varieties that hearken back to the group's name, in the last 20 years rhodolite and tsavorite garnets have gained public appeal. The rising popularity of rhodolite and tsavorite garnets provides a refreshing twist to the January birthstone sales niche, as all garnets are acceptable to wear as the January birthstone. Many who typically turn away from the dark, mysterious colors of pyrope and almandine will find favor with the lighter and more lively pinkish and purplish hues of rhodolite garnets. That is why keeping several red varieties of the stone on-hand is helpful. Tsavorite garnet also holds tremendous value in a jeweler's inventory because of its own beauty and as an affordable and more durable alternative to emerald. |
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History
of...
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Pyrope garnet is perhaps the most easily recognized strain of garnet, and it was very popular in the 18th and 19th centuries under the name "Bohemian Garnet." The stone is widely known as a birthstone and class ring stone. In 1898, the term rhodolite was given to rhododendron-colored garnets found in North Carolina. The name did an excellent job of capturing the rosy color of the stone and is still used today. Tsavorite garnets are found in East Africa and resemble a rare and highly valuable form of garnet called, Demantoid, which was widely used in Victorian jewelry. One can differentiate between tsavorite and demantoid by looking for the horse-tail inclusions that are the signature of a demantoid stone.
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Technical
Specifications:
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| DESCRIPTION |
| Garnet is a group of related minerals. |
| Chemical
Composition: |
Almandite: Fe3Al2(SiO4)3
Grossularite (Tsavorite): Ca3Al2(SiO4)3
Pyrope: Mg3Al2(SiO4)3
Rhodolite: ((Mg,Fe)3Al2(SiO4)3) |
| Appearance: |
Almandite: Transparent to semi-translucent, for very dark stones; reddish orange to red, slightly purplish red to reddish purple, typically dark in tone; may show asterism with a four or six-rayed star
Grossularite (Tsavorite): Usually transparent to semi-transparent; light to dark green, light to dark yellow to reddish orange, colorless (rare)
Pyrope: Transparent to semitranslucent, for very dark stones; medium to dark reddish orange, red through slightly purplish red, colorless (rare); may rarely demonstrate color change from green to reddish purple in stones that are part pyrope and part spessartite
Rhodolite: Transparent; light to dark purplish red to reddish purple |
| Misnomers: |
Almandite: Colorado ruby, Cape ruby, carbuncle
Grossularite (Tsavorite): None known
Pyrope: Colorado ruby, Cape ruby, Arizona ruby, Bohemian carbuncle
Rhodolite: None known |
| Typical
Sizes: |
Almandite: Melee sizes to 10ct; faceted stones up to 40 ct are known
Grossularite (Tsavorite): Melee to 3 ct, largest known faceted stones are 5 ct
Pyrope: Seldom over 2 ct
Rhodolite: Melee sizes to 10 ct; faceted stones up to 100 ct are known |
| Cut Styles: |
Almandite: Faceted, cabochon, beads
Grossularite (Tsavorite): Faceted
Pyrope: Faceted
Rhodolite: Faceted |
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| IDENTIFICATION |
| Optic
Character: |
Almandite: SR, often ADR
Grossularite (Tsavorite): SR, often ADR
Pyrope: SR, often ADR
Rhodolite: SR, often ADR |
| Refractive
Index: |
Almandite: 1.790 (+/-.030)
Grossularite (Tsavorite): 1.740 (+.020, -.010)
Pyrope: 1.714 to over 1.742, 1.74 is normal
Rhodolite: 1.760 (+.010, -.020) |
| Birefingence: |
Almandite: None
Grossularite (Tsavorite): None
Pyrope: None
Rhodolite: None |
| Dispersion: |
Almandite: .024
Grossularite (Tsavorite): .028
Pyrope: None given
Rhodolite: .026 |
| Pleochroism: |
Almandite: None
Grossularite (Tsavorite): None
Pyrope: None, may show color shift due to strong strain
Rhodolite: None |
| Ultraviolet
Fluorescence: |
Almandite: Inert
Grossularite (Tsavorite): Near colorless to light green--inert to weak orange (LW) and weak yellow-orange (SW); yellow--inert to weak orange (LW and SW)
Pyrope: Inert
Rhodolite: Inert |
| Absorption
Spectra: |
Almandite: Usually 3 strong bands at 504, 520, and 573 nm, but may also show fainter lines at 423, 610, and 680-690 nm
Grossularite (Tsavorite): None given
Pyrope: A broad band about 564 nm, cutoff 440 to 445 nm; Fine quality material may show chromium lines in the red end of the spectrum
Rhodolite: Basically the same as the almandite spectrum |
| Cause
of Color: |
Almandite: Iron
Grossularite (Tsavorite): Vanadium with trace of chromium
Pyrope: Iron, chromium
Rhodolite: Iron |
| Specific
Gravity: |
Almandite: 4.05 (+.25, -.12)
Grossularite (Tsavorite): 3.61 (+.12, -.04)
Pyrope: 3.78 (+.09, -.16)
Rhodolite: 3.84 (+/-.10) |
| Polish
Luster: |
Almandite: Vitreous to subadamantine
Grossularite (Tsavorite): Vitreous
Pyrope: Vitreous
Rhodolite: Vitreous |
| Fracture: |
Almandite: Conchoidal
Grossularite (Tsavorite): Conchoidal to uneven
Pyrope: Conchoidal
Rhodolite: Conchoidal |
| Luster: |
Almandite: Greasy to vitreous
Grossularite (Tsavorite): Greasy to vitreous
Pyrope: Greasy to vitreous
Rhodolite: Greasy to vitreous |
| Cleavage: |
Almandite: None; may have indistinct parting
Grossularite (Tsavorite): None; may have distinct parting
Pyrope: None; may have indistinct parting
Rhodolite: None; may have indistinct parting |
| Indentifying
Characteristics: |
Almandite: Needle-like inclusions (usually coarse), zircon crystals with strain halos, and irregular, rounded included crystals of low relief
Grossularite (Tsavorite): Intense green to yellowish green color
Pyrope: Needle-like included crystals and irregular, rounded included crystals
Rhodolite: Color, needle-like crystals (usually coarse), zircon crystals with strain halos, and irregular, rounded included crystals of low relief |
| Known
Enhancements: |
Almandite: None known
Grossularite (Tsavorite): None known
Pyrope: None known
Rhodolite: None known |
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| DURABILITY RATINGS |
| Hardness: |
Almandite: 7-7 1/2
Grossularite (Tsavorite): 7-7 1/2
Pyrope: 7-7 1/2
Rhodolite: 7-7 1/2 |
| Toughness: |
Almandite: Fair to good
Grossularite (Tsavorite): Fair to good
Pyrope: Fair to good
Rhodolite: Fair to good |
| Garnet is sometimes mistaken for: The different garnets of similar colors may be mistaken among species and with ruby, emerald, and tourmaline, depending on color. |
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Care
Tips:
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| Cleaning Methods |
| •Ultrasonic: |
Usually safe; risky if stones contain liquid inclusions |
| •Steamer: |
Risky with tsavorite and pyrope; NEVER steam clean almandite or rhodolite |
| •Warm
soapy water: |
Safe |
| Stability of Stone |
| •Heat
tolerance: |
Abrupt temperature changes may cause fracturing |
| •Light
tolerance: |
Stable |
| •Chemical tolerance: |
Attacked by hydrofluoric acid |
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Recommended
Uses:
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Rings
- Garnets make for beautiful rings and are durable enough to be suitable. They are somewhat vulnerable in a ring setting based on the abuse rings will encounter. It is recommended to be aware that garnet is susceptable to knicks and breaks and care should be taken to prevent damage to this wonderful stone. Try using a tsavorite garnet in a ring as an affordable alternate to emerald. Earrings
- Garnet earrings are a great idea and will attract much attention. Because earrings take less abuse than other types of jewelry, garnet is well suited for earring use. Garnets are in good supply and are relatively inexpensive. Matching sets will not be hard to acquire and are sometimes available in checkerboard cuts. Checkerboard cut garnets in bezel set earrings are quite unique and beautiful.
Pendants - Almandite and rhodolite garnets are most likely the best choices for a garnet pendant due to size availability. The tsavorite and pyrope varieties of garnet rarely come in larger sizes and will be difficult to come by. Based on durability, all varieties of garnet will bode well for a pendant setting.
Bracelet - Although not recommended as the best setting for garnet, bracelets are a viable consideration for the stone. Smaller sized stones would work based on the idea that a smaller stone would have less exposure to abuse and wear. The affordability of garnet, specifically almandite garnet, makes it a great choice for a bracelet containing many stones matched in a set such as a tennis bracelet. If the stones are a deep enough red, they may be considered as an affordable alternative to rubies and a ruby bracelet as described above would be quite the small fortune.
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Source
Map:
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| All technical specifications and care
tips on this page was referrenced from the "Gem
Reference Guide" published by the Gemological Institute
of America |
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