Chemical Formula: Na(Li,Al)3Al6(BO3)3Si6O18(OH)4
Familly: Silicates
Status: IMA-GP
Crystal System: Rhomboedric
Mineral for Display: No
Associated names (luminescent varieties, discredited names, synonymes etc.): rubellite, achroite,UV Type | Main color | Intensity | Observation Frequency |
---|---|---|---|
Long Waves (365nm): | Blue | Mid waves (320 nm): | Yellow | Short Waves (254 nm): | Bluish White | Strong |
Other colors LW: | Bluish White , | ||
Other colors MW: | Yellowish White , | ||
Other colors SW: | Yellowish White , |
Daylight Picture
TOURMALINE;
Photo and Copyright: James Hamblen
Site of the author
Used with permission of the author
Short Waves Pictures (254nm)
TOURMALINE;
UVSW
Photo and Copyright: James Hamblen
Site of the author
Used with permission of the author
Watermelon tourmaline of the Dunton Gem Mine shows luminescence of the red core in intense sky blue. In practice, all Dunton Quarry gem elbaite fluoresce. Although worldwide elbaite does not usually fluoresce, several Maine localities have this characteristic, but few localities have such a high proportion of their elbaite that is fluorescent. Elbaite from Newry with lepidolite replacement may have a creamy yellow fluorescence in both short and long wave UV due to the lepidolite's fluorescence. (see: http://www.mindat.org/photo-188642.html ) Small crystals of achroite from Elba show a classic blue fluorescence under UV at 380nm and a very unusual strong yellow fluorescence under UV at 306nm. The activator is unknown, but achroite contains Mn and a large amount of Mg (15-20%); however, many tourmalines can contain as much Mg without fluorescing. Very small crystals embedded in quartz are only detectable by their strong fluorescence. Other colored tourmalines (pink, yellow and green) from Elba sometimes show very weak yellow luminescence.
(*)Data are not exhaustive and are limited to the most important localities for fluorescence
Images:
http://www.mindat.org/show.php?name=Elbaite
http://webmineral.com/data/Elbaite.shtml
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