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| <<Back to Main | ApatiteApatite | Aquamarine and BerylsAquamarine and Beryls | ChrysoberylChrysoberyl | Crystal CollectionsCrystal Collections | DanburiteDanburite | DiopsideDiopside | EnstatiteEnstatite | Feldspar and MoonstonesFeldspar and Moonstones | FluoriteFluorite | GarnetGarnet | Gemstones in matrixGemstones in matrix | Lapis LazuliLapis Lazuli | PegmatitePegmatite | PeridotPeridot | PetalitePetalite | PhenakitePhenakite | Pyrite, Hematite and Iron OresPyrite, Hematite and Iron Ores | Quartz Family: Amethyst, Citrine, Agate...Quartz Family: Amethyst, Citrine, Agate... | Rare Burmese SpecimensRare Burmese Specimens | RubyRuby | SapphireSapphire | ScapoliteScapolite | Sillimanite or FibroliteSillimanite or Fibrolite | SpinelSpinel | TopazTopaz | TourmalineTourmaline | ZirconZircon | Other Fine CrystalsOther Fine Crystals | | Our Top Tourmaline Highlight | Tourmaline | | Tourmaline occurs in a wide range of colors. It is one of the most favored gemstones for mineral specimens and cut gems collectors due to its incredible variety of colors and the beauty of its crystals. Most tourmalines are known in the gem trade by the variety name following their color:
- Rubellite: Pink to red but also brownish, purplish or orangey, its color is usually due to manganese and iron.
- Verdelite: Yellowish green to bluish green, it is usually colored by iron.
- Indicolite: Violetish to greenish blue.
- Paribas: electric blue typical from Paribas area in Brazil.
- Chrome tourmaline: Intense green color, own its color to chromium.
- Achoite: Colorless. For the mineral collectors, tourmaline group varieties are better known by more scientific names dealing more with the composition and the structure of the stone:
- Dravite: typically yellow to brown can be red also.
- Schorl: Sodium and iron rich, Black.
- Elbaite: Sodium, aluminum, lithium rich, many colors possible.
- Ferridravite: Magnesium and iron rich, Black.
- Chromdravite: Sodium, magnesium and chromium rich, Dark green.
- Buergerite: Sodium and iron rich, Bronzy brown.
- Liddicoatite: Calcium, Lithium, aluminum rich, many colors possible.
Highly saturated tourmalines with fine clarity will be highly priced with some exceptions, such as for Rubellite which even highly included can get high value. Burma (Myanmar) is known for its fine tourmalines, which are mined in Mogok (most varieties), the Molo pegmatic area near Momeik is a lithium and beryllium rich pegmatite area that host very fine Schorl and exceptional fibrous "mushroom" like elbaites) and the Shan and Kayin states (green tourmaline).
But most of the tourmaline commonly in the market is now coming from Brazil and Madagascar. Tourmaline forms as a trigonal crystal in a variety of geological settings; as an associated mineral in metamorphic rocks as gneiss or schist, as long prisms in granitic pegmatite usually with a feldspar matrix, or as single crystals after alteration of the pegmatite resulting, for example, in colonization. In this granite pegmatite it occurs in the immediate vicinity in the enclosing host rocks. Pegmatitic tourmaline is commonly black and is associated with quartz and feldspar.
The light colored gem tourmalines are much rarer, usually occurring in pegmatite core zones. Other occurrences for tourmaline are in hydrothermal veins where heated mineral bearing liquids or gases from deep igneous sources later cooled and crystallized along rock fractures, in granites due to late stage alteration of micas and feldspars by boron containing fluids, and by boron metasomatism in contact and regionally metamorphosed rocks.
Some tourmaline bearing mica schist may have formed by regional metamorphism of argillaceous sediments containing evaporate borates. Because of tourmaline's relatively high hardness and specific gravity, it is often found in alluvial and alluvial deposits as for example in the gravels of Mogok in Burma or in those of Sri Lanka.
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