Fornacite

A variety of Minerals

What is Fornacite?

Fornacite is a rare lead, copper chromate arsenate hydroxide mineral with the formula: Pb2Cu(CrO4)(AsO4)(OH). It forms a series with the phosphate mineral vauquelinite. It forms variably green to yellow, translucent to transparent crystals in the monoclinic - prismatic crystal system. It has a Mohs hardness of 2.3 and a specific gravity of 6.27. It was first described in 1915 and named after Lucien Lewis Forneau (1867–1930) the governor of the French Congo. Its type locality is in Reneville, Republic of Congo. It occurs in the oxidized zone of ore deposits and is associated with dioptase, wulfenite, hemihedrite, phoenicochroite, duftite, mimetite, shattuckite, chrysocolla, hemimorphite, willemite and fluorite.

Market Value Factors

Pricing varies for every rock and mineral, so use these universal factors to gauge Fornacite before comparing listings or appraisals.

Size & Weight

Larger, intact specimens usually command higher prices.

Rarity & Demand

Scarce material or popular varieties sell at a premium.

Condition & Finish

Chips, repairs, and heavy wear lower value; clean prep helps.

Treatment & Provenance

Untreated specimens with documented locality are prized.

Applies to all rocks & minerals.

Quick Facts

Physical Properties

Color: Deep olive-green; golden yellow in transmitted light (small grains).
Hardness (Mohs): 2 - 3
Rock tumbling: Not recommended
Density: 6.3 g/cm³
Streak: Olive green

Chemical Properties

Chemical Formula: Pb₂Cu(CrO₄)(AsO₄)(OH)
Elements: As, Cr, Cu, H, O, Pb

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Fornacite FAQs

How do I identify Fornacite?

Fornacite can be identified by its hardness of 2 - 3 on the Mohs scale, Deep olive-green; golden yellow in transmitted light (small grains). color. Look for these key characteristics when examining specimens.

What color is Fornacite?

Fornacite typically appears in Deep olive-green; golden yellow in transmitted light (small grains).. Color can vary depending on impurities and formation conditions.

How hard is Fornacite?

Fornacite has a hardness of 2 - 3 on the Mohs scale. This makes it a soft mineral that can be scratched easily.