Benitoite
From Freepedia
| Benitoite | |
|---|---|
| Image needed | |
| General | |
| Category | Mineral |
| Chemical formula | BaTiSi3O9 (barium titanium silicate) |
| Identification | |
| Color | Blue; Colorless |
| Crystal habit | Tabular dipyramidal crystals, granular |
| Crystal system | Hexagonal |
| Cleavage | [1011] Poor |
| Fracture | Conchoidal |
| Mohs Scale hardness | 6 - 6.5 |
| Luster | Vitreous |
| Refractive index | 1.757-1.759; 1.802-1.804 |
| Pleochroism | Dichroic (blue to white) |
| Streak | White |
| Specific gravity | 3.6 |
| Melting point | |
| Solubility | Insoluble: HCl, H2SO4 Soluble: HF |
| Diaphaneity | Transparent to translucent |
Benitoite, whose name derives from its type locality (San Benito County, California) is a blue silicate mineral, found in hydrothermally altered serpentinite. Benitoite fluoresces under ultraviolet light, appearing light blue in color.
Contents |
Uses of benitoite
Benitoite's rarity makes it a minor ore for barium or titanium at best. Rather, benitoite's main uses are as a collector's mineral, especially in specimens which show off this mineral's unique crystals, or specimens in which benitoite occurs with its commonly associated minerals. Benitoite's hardness also makes it suitable for use in jewelry, though the general lack of useable material has limited this use.
Associated minerals
Benitoite typically occurs with a rather unique set of minerals, some just as prized by collectors as benitoite itself, along with minerals that make up its host rock. Frequently associated minerals include:
- natrolite, Na2Al2Si3O10 · 2H2O
- neptunite, KNa2Li(Fe, Mn)2Ti2Si8O24
- joaquinite, NaBa2FeCe2(Ti, Nb)2(SiO3)8(OH, F) · 1H2O
- serpentine, (Mg, Fe)3Si2O5(OH)4
- albite, NaAlSi3O8
Alternative names
Benitoide, benitoida, and benitoit are all synonymous with benitoite.
Notes for identification
Benitoite is a fairly rare mineral, found in (at this point) very few locations, most prominently in the Dallas Gem Mine in San Benito County, California, but also in Japan and Arkansas. Finding a blue mineral in these locations is a useful first step in identifying benitoite, but some key attributes should be kept in mind. First, benitoite's crystal habit is fairly unique, and would make a strong aid to identification. The associated minerals are also a key piece of information. Benitoite is typically found with some combination of natrolite, joaquinite, and neptunite on a greenish-grey serpentinite base. Examining pictures of specimens, so that one becomes familiar with the look of this suite, is helpful. Finally, benitoite's fluorescence is a last helpful hint for identification purposes.
