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Datolite
Current inventory:  0 gems
 

Chemistry:  CaBSiO₄(OH)  [Calcium Boron Silicate Hydroxide]

Discovered in 1806 ;   IMA status: Valid (pre-IMA; Grandfathered).
Datolite is named from the Greek word dateisthai meaning to divide in reference to the granular nature of the massive variety.

Classification

Mineral Classification:

Silicates

Nickel-Strunz 10th Ed. ID:

9.AJ.20

9 : SILICATES (Germanates)
A : Nesosilicates
J : Nesosilicates with BO₃ triangles and/or B[4], Be[4] tetrahedra, cornersharing with SiO₄
(Gadolinite-Datolite Group)

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Crystals typically short prismatic to wedge shaoed tabular, to 12 cm with complex faceted terminations. Also in porcelain-like masses or nodules; botryoidal or globular, having columnar structure; granular to compact; cryptocrystalline.

Twinning:

None

Physical Properties

Cleavage:

None

Fracture:

Conchoidal to Irregular/Uneven

Tenacity:

Brittle

Hardness (Mohs):

5.0 - 5.5

Density:

2.96 - 3.00 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, White, Brown, Yellow, Light Green

Transparency:

Transparent to Translucent, nearly Opaque

Luster:

Vitreous, Resinous

Refractive Index:

1.626 - 1.670  Biaxial ( - )

Birefringence:

0.0440

Dispersion:

Very Weak to None; r > v

Pleochroism:

X = Colorless, Y = Colorless, Z = Colorless

Occurances

Geological Setting:

A secondary mineral in mafic igneous rocks; in geodes in tuffs; in skarns in limestones; in serpentinites and hornblende schists; from some ore veins.

Type Locality:

Arendal, Aust-Agder, Norway

Year Discovered:

1806

View mineral photos:

Datolite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Datolite is a rare collector's gem not often seen in the gem market. Faceted gems are very brilliant even though their dispersion (fire) is low. It is often found in basalt vesicles along with Calcite and Zeolites and is often confused with certain Zeolites because of its luster, color and associations.

Although sources are worldwide, many Datolite gems come from US material. US sources are Hampden County, Massachusettes; Hartford County, Connecticut; Essex County and Passaic County, New Jersey; Loudoun County, Virginia. Worldwide sources are Arendal, Norway (the Type Locality); Harz Mountains, Germany; Italy; Habachtal, Austria; Iwato Copper Mine, Japan; Charcas, San Luis Potosi, Mexico and exceptional, pale yellow crystals from Dal'negorsk, Primorskiy Kray, Russia.

Datolite is also found in the Lake Superior region of Michigan. It is associated with native copper at this location and is found in porcelain-like masses and nodules. The nodules are brown to off white in color and some are cut and polished as an ornamental stone.
 

  
Datolite gems for sale:

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