Natural Dioptase Specimen — Mfouati District, Republic of the Congo

A superb example of one of the mineral world’s most coveted green crystals. This natural, untreated dioptase specimen displays an intense, almost electric emerald-green colour with exceptional surface lustre — the hallmark of a high-quality Congo locality piece. A standout addition to any mineral collection.

Specimen Details

• Mineral: Dioptase (Cu₆[Si₆O₁₈]·6H₂O)
• Dimensions: 58 × 45 × 24 mm
• Weight: 64 g
• Locality: Mfouati District, Bouenza Department, Republic of the Congo
• Colour: Intense emerald-green to deep teal-green
• Lustre: Vitreous to sub-adamantine — highly lustrous
• Treatment: Natural and untreated
• You receive: The exact piece shown

Geology of Dioptase

Dioptase is a rare copper cyclosilicate mineral with the chemical formula Cu₆[Si₆O₁₈]·6H₂O. It forms in the oxidation zones of copper ore deposits, typically in arid environments where copper-rich groundwater reacts with silica to produce vivid emerald-green to blue-green prismatic crystals. Its crystal system is trigonal, and it belongs to the cyclosilicate subclass — the same structural group as beryl and tourmaline.

• Crystal system: Trigonal (rhombohedral)
• Hardness: 5 on the Mohs scale
• Cleavage: Perfect in three directions — rhombohedral
• Specific gravity: 3.28–3.35
• Lustre: Vitreous to sub-adamantine
• Transparency: Transparent to translucent
• Streak: Pale green
• Associated minerals: Malachite, chrysocolla, quartz, calcite, wulfenite
• Formation environment: Secondary oxidation zones of copper sulphide deposits
• Notable localities: Mfouati (Congo), Tsumeb (Namibia), Altyn-Tyube (Kazakhstan), Bisbee (Arizona, USA), Mindouli (Congo)

History & Discovery

Dioptase was first described in 1797 by the French mineralogist René-Just Haüy, who named it from the Greek words dia (through) and optomai (to see) — a reference to the visible cleavage planes visible through the crystal faces. Before its formal identification, specimens from Kazakhstan were mistakenly believed to be emeralds due to their near-identical colour, and were reportedly sent to the Russian Imperial Court as such.

The Republic of the Congo — particularly the Mfouati and Mindouli districts of the Bouenza and Pool Departments — has been one of the world’s premier dioptase localities since the 20th century, producing specimens of exceptional crystal size, colour saturation, and matrix quality that are prized by museums and private collectors worldwide.

Crystal Properties & Metaphysical Use

Dioptase is associated with the heart chakra and is regarded in crystal healing traditions as one of the most powerful stones for emotional renewal and forgiveness. Its vivid green resonance is said to dissolve old emotional wounds, encourage compassion, and reconnect the holder with a sense of abundance and joy.

• Chakra: Heart (4th)
• Zodiac: Scorpio, Sagittarius, Virgo
• Element: Water
• Key properties: Emotional healing, forgiveness, compassion, abundance, living in the present moment
• How to use: Place on the heart during meditation, display in a healing space, or hold during breathwork to release emotional tension

Perfect For

• Mineral collectors seeking a high-quality Congo locality piece
• Crystal healers working with heart chakra energy
• Collectors of rare copper-bearing minerals
• Thoughtful gifts for geology enthusiasts or spiritual practitioners
• Display in a home office, study, or meditation space

Care Notes

• Dioptase is relatively soft (Mohs 5) — handle with care and store separately from harder minerals
• Avoid water immersion — the copper content can leach and the crystal structure is sensitive to moisture
• Keep away from direct sunlight to preserve colour intensity
• Dust gently with a soft dry brush

Natural Specimen Notice

As a natural mineral specimen, minor surface variations, matrix inclusions, or contact marks are inherent to the piece and not considered defects. Please review all photos carefully before purchasing.

Need additional photos or have a question? Contact us — we’re happy to help.

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