Information about Datolite

Datolite is an attractive calcium borosilicate mineral that forms in a wide range of habits – from sharp, well-developed glassy prismatic crystals of pale green, white, or colourless transparency, to massive porcelain-like nodules.

As distinct crystals, datolite typically forms wedge-shaped to prismatic monoclinic crystals with a vitreous lustre and a greasy appearance on fracture surfaces. They are most commonly colourless to white or very pale yellow-green, though copper-stained examples can be pale green. The crystals are typically found in the vesicles of basaltic and other mafic rocks, in hydrothermal veins, and in contact metamorphic skarns, in company with calcite, prehnite, apophyllite, native copper (in Michigan), and zeolite minerals.

Datolite’s name derives from the Greek dateisthai (to divide) – a reference to the granular texture of massive forms, which appears to divide easily under mechanical stress.

Uses and History

Datolite was first described in 1806 by the Norwegian mineralogist Jens Esmark, from specimens collected at Arendal in Aust-Agder, Norway. It has been recognised as a mineral species for over two centuries and is a well-established collector mineral.

In Michigan, USA, the copper-bearing basalts of the Keweenaw Peninsula have produced datolite nodules of extraordinary beauty: dense porcelain-like masses up to tens of centimetres across, their white calcite-like datolite base stained and blotched with vivid copper-greens (from native copper and secondary copper minerals), sometimes also with pink (from cobaltite), creating an irreplaceable lapidary material used for cabochons and carvings. These Michigan nodules are among the most sought-after and recognisable collector and lapidary materials from the Great Lakes copper district.

Crystal localities producing fine transparent specimens include Arendal in Norway; the diabase trap rocks of New Jersey and Connecticut, USA; Trentino in northern Italy; the Bor district in Serbia; and various German and Czech skarn localities.

Mineralogy

Hazards and Warnings

No specific toxicological hazards are associated with datolite under normal handling conditions. Standard dust precautions apply when cutting.

Almost all rocks, minerals (and, frankly, almost all other substances on earth) can produce toxic dust when cutting, which can cause serious respiratory conditions including silicosis. When cutting or polishing rocks, minerals, shells, etc, all work should be done wet to minimise the dust, and a suitable respirator or extraction system should be used.

Translations

Further Reading / External Links

• https://en.wikipedia.org/wiki/Datolite
• https://www.mindat.org/min-1213.html
• https://www.handbookofmineralogy.org/pdfs/datolite.pdf