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| Frequently Asked Questions |
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| What is tourmaline? - Tourmaline is a group of minerals now divided into fourteen different mineral species. The change in the various names is summarized by King (2002). The original name, turamali, comes from the native language, Cingalese, in Sri Lanka. Unusual transparent red, pink, pale brownish yellow, and light greenish brown gem pebbles were found in the gem-bearing gravels of that country and when the unknown gem materials were received in the Netherlands in 1703 and afterwards, gem merchants began to notice the unusual properties of a new gem. By 1772, the French mineralogist Romé de Lisle discovered that tourmaline, was essentially the same as an opaque, generally black mineral called schörl. |
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Elbaite from Dunton quarry showing steep termination
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| By 1888, there was still some debate over whether tourmaline and schörl, and a new commer "dravite", named in 1883, should be separate species or should they merely be thought of as varieties of one mineral called tourmaline. Robert Riggs of the U. S. Geological Survey then wrote about his chemical studies of the kinds of tourmaline and he proposed that lithia tourmaline be the name for the brightly colored tourmalines found in granite pegmatites. His studies used specimens from Maine and elsewhere. |
| In 1913, the Russian mineralogist, W. Vernadsky, proposed that lithium tourmaline be called elbaite after the famous tourmaline location in Elba, Italy. Most of Maine's brightly colored gem tourmaline is today known as the species elbaite, however, some pink and nearly colorless Maine tourmalines at Black Mountain quarry in Rumford, Maine and at Mount Mica quarry in Paris, Maine have been identified as the tourmaline called rossmanite (Wise and Brown, 1992; Hawthorne and Henry, 1999, Simmons et al., 2004). |
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Foitite Snow Falls road cut with Paris
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Rossmanite is a tourmaline which is poor in lithium, but which in most other respects is similar to elbaite. These two minerals are visually identical. In 1993, another new species of tourmaline, foitite, was found that was deficient in alkali metals and was rich in iron. This mineral is usually found in pegmatites and was soon reported from Maine by King and Foord (1994, 2000) and Wise (1999) at Mount Mica quarry and Emmons quarry, Greenwood. The original foitite was from a dark purple to steely blue to dark blue zone in a pegmatite pocket tourmaline crystal in San Diego County, California, but there are now many more examples of black or dark brown foitite. The color arises from what is called "anomalous interference". Microscopic study of Maine gem pocket tourmalines show that similar tiny dark purple to steely blue zones are found also at the Fisher quarry, in Topsham, Maine.
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| The reason there are 14 tourmaline species is that each has a slightly different chemical combination, even though the crystal structure is identical. All tourmalines contain silicon, boron, aluminum, and hydroxyl or fluorine. The ratios of various metals and alkali metals and their roles in the tourmaline crystal structure are the reasons that there are different species (See Gaines, et al., 1997; Simmons, 2002). To date, there are five different tourmalines found in Maine: schörl, the common black or blue tourmaline; dravite, a black or brown tourmaline found in schists or metal ore deposits; elbaite, a green, pink, red, colorless, or blue tourmaline; foitite, a generally black but sometimes purple tourmaline; and rossmannite, a generally pink, red, or colorless tourmaline. |
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Etched elbaite showing thin filaments of left-over tourmaline after most of it was etched out of a part of a crystal.
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| What is a species? What is a variety? What is a group? Mineral collectors, as well as professional mineralogists, are sometimes uncertain about definitions. The modern chemical classification of minerals was greatly improved by Swedish mineralogist Jön Jakob Berzelius in 1814 with the publication of his systematic mineralogy book. By 1853, James Dwight Dana had further modified the classification of minerals and that is essentially the one that has continued to be used worldwide. |
| A species is the unit of classification. Species, singular or plural, has/have a definite chemical formula and a specific crystal structure. When a species has a minor variation due to color, texture, chemical composition, it has sometimes been given a name, but the name is a variety of some species. Red or pink tourmaline has been called rubellite, while green tourmaline has been called verdelite, colorless tourmaline has been called achroite, and blue tourmaline has been called indicolite. However, these color varieties may not all be the same species. The tourmaline variety is based on the color while the species is based on structural chemistry. There are at least four tourmaline species which have been called rubellite and at least three species of tourmaline have been called indicolite. |
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Dunton tourmaline crystal showing achroite zone.
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| When there are three or more species which have essentially the same crystal structure and can mutually vary chemically, they are grouped together. Two species can for a series, while three are called a group. The zeolite group is an exception where the minerals are put together because they have some important similarities, but there are very different crystal structures present in the group.
The various groups which all have similar chemical building blocks are put together in a class. All silicates are in the same chemical class. Phosphates, arsenates, and a few other chemical building blocks which are otherwise similar have been placed in a single class. Similarly sulfates and some other similar chemical building blocks have been placed in a single chemical class. There are some rare cases when there are minerals which could be in the same group, but the individual species would otherwise belong to different chemical classes. The jarosite group would be an example of this exception. All of these materials are implicitly part of the Mineral Kingdom.
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What is the Mineral Kingdom? Essentially the part of the earth not changed by living materials. When biologically produced materials are no longer recognizable as fossils by their having been dissolved, recrystallized, etc. by the elements of nature, materials which were once part of other kingdoms may become minerals, just as living things ingest minerals to recreate themselves. There can be a cycle of materials changing from one kingdom's classification to another. A shell fragment would be a fossil while a crystal of calcite whose chemicals had passed through the biological processes would be a mineral.
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Dunton elbaite showing white thread-like healed fractures. The healing "cement" is also tourmaline
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| There is yet to be a convenient place to put materials created through human intervention, however, automobiles converted to mixtures of goethite and lepidocrocite have not been accepted as minerals although the components of rust also occur as minerals. Similarly, synthetic ruby is not classed as a mineral although it is a gem. |
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