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Chemical Formula | SiO2 | ||||||||||||||||
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Composition | Silicon dioxide. Its purple coloring is caused by impurities of iron or manganese compounds. | ||||||||||||||||
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Color | Light to dark purple. May be banded purple and white, or mixed together with colorless Rock Crystal; and may also be mixed with brownish-yellow Citrine. | ||||||||||||||||
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Streak | White | ||||||||||||||||
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Hardness | 7 | ||||||||||||||||
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Crystal Forms and Aggregates |
(Hexagonal) Often occurs as protruding clusters of
pyramids on a geode base. These "pyramids" can be
quite large. Also occurs as tall prismatic crystals, as short stubby crystals, in drusy aggregates, massive, in geodes, and as rounded waterworn stones. A very
interesting but strange habit is as crystalline crusts inside volcanic pipes. Crystals are usually striated horizontally, and occasionally have a scepter growth. |
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Transparency | Transparent to translucent | ||||||||||||||||
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Specific Gravity | 2.6 - 2.7 | ||||||||||||||||
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Luster | Vitreous | ||||||||||||||||
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Cleavage | Indiscernible | ||||||||||||||||
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Fracture | Conchoidal | ||||||||||||||||
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Tenacity | Brittle | ||||||||||||||||
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Other ID Marks | May fluoresce cream or white in shortwave ultraviolet light | ||||||||||||||||
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Varieties |  Amethyst Quartz - Mixture
of Amethyst and Milky Quartz (or clear Quartz). It is purple on
top and white or clear on the bottom. It may also be banded purple and white. Ametrine
- Mixture of Amethyst and Citrine. It is partially purple and partially
orange-yellow, with the color zones often sharply
divided. Canadian
Amethyst - Amethyst with an internal coating of
red Hematite, found in Thunder Bay, Ontario. Lavender
Amethyst - Pale purple variety of Amethyst Veracruz
Amethyst - Tall, prismatic Amethyst crystals from Vera Cruz, Mexico. |
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In Group | Silicates ; Tectosilicates ; Silica group May also be classified as an oxide (Oxides ; Simple Oxides) |
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All About | Amethyst is a well known gem. It is variety of Quartz, which contains many other gemstones, such as Citrine, Smoky Quartz, and Rock Crystal. The color of Amethyst specimens from certain localities slowly fade upon prolonged exposure to light. Much Citrine is artificially formed by heat-treating Amethyst. | ||||||||||||||||
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Uses | Amethyst is one of the most popular gems. It
has a beautiful color and is rather common, making it an
inexpensive, widely used gem. Most Amethyst is faceted
into jewelry cuts, and some are cut as cabochons. Large, massive chunks of Amethyst banded with Quartz is sometimes carved into
ornaments. Amethyst is also popular among mineral collectors. Small geode sections and tumbled stones are sold to amateur collectors, while more experienced collectors go for the rare prismatic crystals and giant geode sections. |
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Striking Features | Color and crystal habits | ||||||||||||||||
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Popularity (1-4) | 1 | ||||||||||||||||
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Prevalence (1-3) | 1 | ||||||||||||||||
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Demand (1-3) | 1 | ||||||||||||||||
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Distinguishing Similar Minerals |
Garnet - occurs in very different
crystals Fluorite and Apatite - much softer (4 and 5) Spinel - occurs in different crystals, harder (7½ - 8) |
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Commonly Occurs With |
Other types of Quartz | ||||||||||||||||
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Noteworthy Localities |
Amethyst is a very common mineral and is found worldwide. Only a select few of the most famous localities will be mentioned here. Tall, prismatic, well-shaped crystals are restricted to two Mexican localities: Piedras Parado and Las Vigas de Ramirez, Veracruz; and Amatitlan, Guerro. They occur in elongated crystals that are rarely faceted, since collectors pay well for these rarities, as most other Amethyst is in drusy, stubby, pyramidal clusters. Enormous quantities of fine Amethyst come from Minas Gerais, Brazil. Also in Brazil is the famous Rio Grande do Sul, where the enormous crystal-lined Amethyst geodes are found, especially in Ametista do Sul. Another South American country, Uruguay, produces deeply colored crystals in large geodes and pipes in Artigas, near the Brazilian border. Another good South American locality, which is especially noted for Ametrine, is the Anahi Mine, Santa Cruz, Bolivia. Very dark and clear material comes from the Ural Mountains and Siberia in Russia. Large amounts of Amethyst are found both Namibia and South Africa - these are often labelled in the jewelry industry as "African Amethyst. In Namibia a famous occurence is the Goboboseb Mountains, near Brandberg, in the Erongo Mountains of Namibia. In South Africa, extensive deposits are in the Magaliesberg Mountains in Pretoria and in the Boekenhoutshoek area in the Mkobola district, South Africa. There are two notable Canadian occurrences. One is Thunder Bay, Ontario, where specimens contain an internal coating of red Hematite. The other locality is the area of Digby, Nova Scotia, where naturally rounded, waterworn Amethyst pebbles are found on the beaches along the Bay of Fundy. In the U.S., fine Amethyst crystals can be found in Four Peaks (in the Mazatzal Mountains), Gila Co., Arizona; in the Pohndorf Mine, Jefferson Co., Montana; in the Pennoyer Mine at Redfeather Lakes, Larimer Co., Colorado; Deer Hill, Maine; There are several good localities in the Carolinas, specifically Statesville, Iredell Co., North Carolina; the Reel Mine, Iron Station, Lincoln Co., North Carolina; and Abbeville Co., South Carolina (Diamond Hill Quartz Mine and the Ellis Jones Mine). A recently productive location producing deep puple crystals is Jacksons Crossroads, Wilkes Co., Georgia. Diamond Hill in Ashaway, Hopkinton, Washington Co., Rhode Island is famous for the rare scepters that were found there. Good Amethyst is also found in the traprock quarries of Passaic Co., New Jersey, specifically at the Upper New Stree Quarry in Paterson and at Prospect Park. |
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Picture Icon Links |
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Picture Links | 1. Stubby Amethyst crystals 2. Small Amethyst crystal cluster 3. Amethyst Geode 4. Tall, prismatic Amethyst crystals 5. Grouping of Amethyst crystals 6. "Canadian Amethyst" 7. Naturally rounded Amethyst 8. Ametrine |
