How do I identify Talmessite?

Talmessite can be identified by its hardness of 5 on the Mohs scale, White color. Look for these key characteristics when examining specimens.

What color is Talmessite?

Talmessite typically appears in White, colorless, translucent pale green (nickelian), brownish pink (cobaltian). Color can vary depending on impurities and formation conditions.

How hard is Talmessite?

Talmessite has a hardness of 5 on the Mohs scale. This gives it moderate hardness.

Talmessite

A variety of Minerals

What is Talmessite?

Talmessite is a hydrated calcium magnesium arsenate, often with significant amounts of cobalt or nickel. It was named in 1960 for the type locality, the Talmessi mine, Anarak district, Iran. It forms a series with β-Roselite, where cobalt replaces some of the magnesium, and with gaitite, where zinc replaces the magnesium. All these minerals are members of the fairfieldite group. Talmessite is dimorphic with wendwilsonite (which is not a member of this group).

Talmessite Market Value Calculator

Estimate the market value of Talmessite using size, quality, and finish. This preview calculator is for quick context and is not a formal appraisal.

Talmessite Localities Map

See where Talmessite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.

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North ZoneCentral RidgeSouth Basin

Key Characteristics

Characteristics of Talmessite

Talmessite is a moderately hard mineral, with Mohs hardness 5, harder than fluorite but not as hard as quartz. The specific gravity calculated from the formula and the cell dimensions is 3.49, but the measured value is less for ordinary talmessite, at 3.42 and more for the cobaltoan variety, at 3.57. The mineral displays polysynthetic twinning. It is not radioactive and it loses water of crystallisation at 450.

Appearance of Talmessite

Talmessite occurs as prismatic crystals to 3 mm, as radiating fibrous aggregates or as fine crystalline aggregates; it may also be stalactitic or in crusts. Pure talmessite is white or colourless, and colourless in transmitted light, but nickel-rich varieties are pale green and cobalt-rich varieties may be brownish, pink or the purple colour typical of many cobalt minerals. The streak is white and crystals are transparent to translucent with a vitreous lustre.

Formation of Talmessite

Talmessite is a rare secondary mineral formed typically in the oxidized zone of some hydrothermal mineral deposits, as an alteration product of realgar, orpiment, or Cu–Ni arsenides. Cobalt-rich varieties are found in the oxidised zone of cobalt arsenide deposits. It occurs associated with gaitite, erythrite, annabergite, picropharmacolite, pharmacolite, austinite, fluorite, baryte, aragonite, calcite and dolomite. At the type locality it is associated with aragonite and dolomite.