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Chemical Formula | Ca2(Mg,Fe)5Si8O22(OH)2 | ||||||||
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Composition | Basic calcium, magnesium, iron silicate | ||||||||
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Color | White, light to dark gray, light yellow, light to dark green, light pink to light purple. Rarely colorless. | ||||||||
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Streak | Colorless | ||||||||
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Hardness | 5 - 6 | ||||||||
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Crystal Forms and Aggregates |
(Monoclinic) Long , prismatic crystals occur, as do bladed, columnar, fibrous, and acicular forms. Also occurs radiating, as wheat sheaf formations, and as tough interlocking fibers which may appear massive. The fibrous variety is very flexible and elastic. | ||||||||
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Transparency | Translucent | ||||||||
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Specific Gravity | 2.9 - 3.2 | ||||||||
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Luster | Vitreous, silky | ||||||||
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Cleavage | 2,2 - prismatic | ||||||||
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Fracture | Uneven and/or splintery | ||||||||
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Tenacity | Brittle. Some fibrous specimens elastic. | ||||||||
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Other ID Marks | Many specimens fluoresce, usually white or yellow | ||||||||
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Varieties | Note: Some of these varieties are also
varieties of other amphibole minerals. Amianthus
- Old name applied to any asbestos (i.e. fibrous) mineral of the amphibole group Asbestos
- Any extremely fibrous mineral. When it is applied to Tremolite,
it is referring to the fibrous variety. Asbestos
Amphibole - Term applied to any fibrous mineral of the amphibole group, including Tremolite. Byssolite
- Actinolite or Tremolite composed of tiny, interwoven, fibrous crystals; creating a tough mass Chrome-tremolite
- Tremolite containing chromium, giving it a deep green
color Hexagonite
- Light pink to light purple Tremolite found in St.
Lawrence Co., New York Mountain
Leather or Mountain Cork - Name
applied to fibrous minerals of the amphibole group composed of a mat-like felt of fibers that look and feel like knitted cloth. Nephrite - Variety of Actinolite/Tremolite
made up of tough, hard, interwoven fibers. The content of iron and magnesium are
about equal in Nephrite. Tirodite
- Tremolite with inclusions of manganese oxide dendrites. |
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In Group | Silicates ; Inosilicates ; Amphibole group | ||||||||
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All About | The amount of iron and magnesium varies
among Tremolite specimens. If a mineral has more than two
percent of iron in the structure (which is replaced by magnesium), then it
is not Tremolite, but Actinolite. Tremolite and Actinolite share
the same chemical formula, but Actinolite has a greater
presence of iron over magnesium, whereas Tremolite has a
greater presence of magnesium over iron. Because they
share the same formula, there are varieties that belong
to both of them. Mountain Leather, a fibrous varieties of Tremolite, has a silky luster, a soft, felt-like feel, and the fibers can be moved around. The other fibrous variety, Nephrite is made up of tough, interlocking fibers, so dense that the fibers are not discernible. Any translucent Nephrite specimen that has an interesting or uniform color distribution and is extremely tough fits under the category of Jade. Asbestos Tremolite should never be brought near the mouth. If its fibers or particles enter the lungs, they can cause asbestosis. Asbestosis is a lung disease caused by inhalation of asbestos particles, which causes several cancers, particularly lung cancer and mesothelioma (an inoperable cancer of the chest and abdominal lining). Symptoms of asbestosis do not arise until about 20 years after the inhalation. Washing hands after handling specimens is highly recommended. Many mineral collectors avoid collecting asbestos because of the hazards. |
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Uses | The finely fibrous variety of Tremolite is
used for industrial asbestos. Although fibrous Serpentine is the main source of asbestos,
Actinolite is a great contributor. Because it is not
affected by fire and is a poor heat conductor, it is used
in fire retardant devices and for heat protection. Its
former use, which has been outlawed in most areas, was as
an insulator, but has been banned because of its
notorious nature of causing cancer and other long term
illnesses. Nephrite is one of the minerals that form the important gem Jade. Jade is cut into cabochons, beads, and earrings. Rings and bracelets are sometimes carved out of an entire mass of Jade. Valuable ornamental sculptures and figures are also carved from this gem. Nephrite is only one form of Jade; the other form is the more valuable Jadeite. |
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Striking Features | Crystal habit and cleavage angle of amphiboles | ||||||||
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Complex Tests | Insoluble in acid | ||||||||
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Popularity (1-4) | 2 | ||||||||
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Prevalence (1-3) | 2 | ||||||||
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Demand (1-3) | 1 | ||||||||
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Distinguishing Similar Minerals |
Tourmaline - lacks cleavage, harder (7 - 7½) Wollastonite - softer (4½ - 5), different cleavage angle, usually fluorescent Epidote - different cleavage angle, crystals are more glassy Actinolite - no distinction can be made without x-ray equipment |
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Commonly Occurs With |
Albite, Barite, Chlorite, Epidote, Muscovite, Serpentine, Calcite, (Marble) | ||||||||
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Noteworthy Localities |
Tremolite has many good localities, but only
the finest will be mentioned here. Large prismatic crystals and crystal clusters occur at Haliburton and Wilberforce, Haliburton Co., Ontario, where they fluoresce white. Tremolite also occurs in the St. Lawrence Co. area in New York, but in Fowler and DeKalb (St. Lawrence Co.) the lilac variety, known as Hexagonite, is abundant. White, fibrous masses occur at Ossining and Anthony's Nose, Westchester Co., New York, and white and greenish crystals have were found at Cannan, Litchfield Co., Connecticut. Other U.S. occurrences are the French Creek mine, Chester Co., Pennsylvania; and Feather river, Butte Co., California. In Europe, fine specimens were collected at Piemonte, Italy, and in the Tremola Valley, Switzerland. See also Nephrite for additional localities. |
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Picture Icon Links |
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Picture Links | 1. Tremolite
crystal mass 2. Asbestos Tremolite 3. Hexagonite 4. Nephrite Jade |
