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Complex Datolite Crystal Cluster

The Mineral datolite




Datolite forms in very attractive crystals that can be highly lustrous and very sparkly, or have frosted crystal faces. A totally different form of Datolite are the oval-shaped nodules that lack any distinctive crystal form. These nodules can be sliced and polished to show beautiful coloring and patterns within the nodule. Nodules are often colored by Copper inclusions which can give them a reddish color.

Datolite was named in 1806 by Jens Esmark, a Danish-Norwegian professor of mineralogy, for the Greek term "dateishai", which means to divide, alluding to the often grainy aggregates of Datolite which break easily.
Chemical Formula CaBSiO4(OH)
Composition Basic calcium borosilicate
Color Most commonly light green, also minty green, dark green, yellowish green, yellow, white, and colorless. Rarely red or pink from Hematite or manganese inclusions. Nodular forms may be white, gray, beige, orange, pink, red, brown, and yellow, and are often multicolored or have lighter and darker color zones.
Streak Colorless
Hardness 5 - 5.5
Crystal System Monoclinic
Crystal Forms
and Aggregates
In distinct short but stubby crystals with many crystal faces and angles. Often in interlocking groups of crystals, platy, drusy, and as crystal plates linings vugs and geodes. Also forms in earthy and botryoidal nodules. May also form as an epimorph after Anhydrite and Glauberite of hollow crystal casts.
Transparency Transparent to nearly opaque
Specific Gravity 2.8 - 3.0
Luster Vitreous, waxy, dull
Cleavage None
Fracture Conchoidal to uneven
Tenacity Brittle
In Group Silicates; Nesosilicates
Striking Features Crystal shape, color, and mode of occurrence.
Environment In cavities of basalt and diabase seams.
Rock Type Igneous
Popularity (1-4) 2
Prevalence (1-3) 2
Demand (1-3) 2


Datolite AUCTIONS

VARIETIES
 -  Uncommon botryoidal form of Datolite.
 -  Geode with Datolite from Tiso (Teis) in Italy.


USES
Datolite is used a collector's gemstone, and the nodules from Michigan are sliced and polished as ornamental stones and minor gemstones. Datolite is mined in Russia as a source of boron.

NOTEWORTHY LOCALITIES
The premier locality for Datolite, forming huge, well-shaped crystals is the Bor Pit, Dal'negorsk, Primorskiy Kray, Russia. Datolite lining vugs and geodes come from Tiso (Teis) in Italy, and are known locally as Teis Spheres. An unusual manganese-rich, pink variety of Datolite comes from the Kalahari Manganese Field of South Africa at the Wessels Mine in Hotazel and the N'Chwaning Mines in Kuruman. In Mexico, large, lustrous crystals associated with Danburite come from Charcas, San Luis Potosí, Mexico.

In the U.S., some of the best Datolite crystals come from the Roncari Quarry, East Granby, Hartford Co., Connecticut. Large crystals are well-known from the Lane Quarry, Westfield, Hampden Co., Massachusetts. The traprock quarries of Northern New Jersey have also produced excellent examples of Datolite, with some of the more prolific producers mentioned below: Large, well formed crystals have come both Prospect Park and Paterson, Passaic Co. Gemmy green Datolite crystal plates have from the Braens Quarry, Haledon, Passaic Co; and platy lustrous crystals from the Millington Quarry, Somerset Co. A classic locality is Bergen Hill, Hudson Co.; where Datolite occurred in diabase seams.

Porcelainous Datolite nodules that are often sliced and polished for collectors are unique to the Keweenaw Peninsula Copper Mining District in Michigan. These mineralogical oddities come in a range of colors and patterns, and are found in many of the Copper mines in the region. Some of the more notable mines in that area include the Centennial Mine, Hancock Mine, and Quincy Mine, in Houghton Co.; the Copper Falls Mine, Clark Mine, Delaware Mine, and Keweenaw Point in Keweenaw Co.; and the Caledonia Mine, Flintsteel Mine, and the Mass Mine, in Ontonagon Co.

COMMON MINERAL ASSOCIATIONS
Calcite, Prehnite, Stilbite, Heulandite, Apophyllite, Quartz, Copper, Babingtonite

DISTINGUISHING SIMILAR MINERALS
Quartz - Forms in different crystals, greater hardness.
Titanite - Crystals more pointed and elongated, higher specific gravity.
Howlite - Differs from Datolite nodules with a lower hardness, and different environment. Also lacks colored examples.


datolite PHOTOS
 
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