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Formula: Cu2BO(OH)5
Monoborate
Crystal System: Orthorhombic
Specific gravity: 3.28 measured, 3.303 calculated
Hardness: 2
Streak: Pale blue
Colour: Bright blue
Luminescence: Not fluorescent under UV
Solubility: Dissolves quickly in dilute hydrochloric acid
Environments
Localities
At the type locality, the Tachgagalt Mine, Tansifte Caïdat, Agdz Cercle, Zagora Province, Drâa-Tafilalet Region,
Morocco, jacquesdietrichite occurs as transparent bright-blue blades, sometimes intergrown into broader tablets,
and as aggregates of pale-blue scales. It is found in small cavities in
gaudefroyite-calcite rock and as
inclusions in calcite. Blades do not exceed 0.5 mm in length and 0.02 mm in
thickness, and often taper somewhat in thickness from tip to base. Blades are slightly flexible with irregular
fracture and exhibit one perfect and very easy cleavage and two good cleavages.
Jacquesdietrichite is the only known mineral containing the BO(OH)2 group and its structure is not
closely related to any other known borate mineral
(EJM 16.2.361-366).
Jacquesdietrichite is probably formed as a secondary,
low-temperature product of hydrothermal reworking of boron-bearing
manganese-oxide ore. Associated minerals include
henritermierite,
gaudefroyite and calcite
(HOM).
At the Caledonia Mine, Mass City, Ontonagon County, Michigan, USA, bulbous blue jacquesdietrichite occurs with
green malachite and colourless gel-like
datolite on copper
(Mindat photo).
Jacquesdietrichite from the Caledonia Mine -
Image
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