Ultra Rare Turquoise Gunheath China Clay Mine Cornwall Genuine Specimen with Hand Signed Premium Certificate of Authenticity

Ultra Rare Turquoise – Gunheath China Clay Mine, St Austell, Cornwall, England

This Ultra Rare Turquoise specimen from the Gunheath China Clay Mine, St Austell, Cornwall, England, is a genuine and carefully selected example of British secondary copper mineralisation. The photograph provided shows the exact specimen you will receive. Please refer to the images for full sizing details and accurate scale.

This crystal includes a fully hand-signed Premium Certificate of Authenticity confirming its genuine origin and locality.

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Mineral & Geological Classification – Turquoise

Turquoise is a hydrated copper aluminium phosphate mineral with the chemical formula CuAl₆(PO₄)₄(OH)₈·4H₂O. It belongs to the phosphate mineral group and crystallises in the triclinic crystal system, although it is most commonly found in microcrystalline or massive form rather than well-defined crystals.

Mineral Name: Turquoise
Chemical Formula: CuAl₆(PO₄)₄(OH)₈·4H₂O
Mineral Group: Phosphate
Crystal System: Triclinic
Hardness: 5–6 on the Mohs scale
Lustre: Waxy to subvitreous
Transparency: Opaque

Turquoise is recognised for its distinctive blue to blue-green colour, produced by copper content. Variations in aluminium, iron and other trace elements can influence tonal differences, resulting in sky blue, greenish-blue or deeper teal shades.

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Geological Setting – Gunheath China Clay Mine, St Austell

Gunheath China Clay Mine lies within the St Austell granite district of Cornwall, part of the Cornubian Batholith formed during the late Carboniferous to early Permian periods. This granite intrusion generated extensive hydrothermal systems and later deep weathering that produced economically significant kaolin (china clay) deposits.

Turquoise in Cornwall forms as a secondary mineral in the oxidised zones of copper-bearing deposits. It develops when copper-rich solutions interact with aluminium and phosphate sources within weathered granite and surrounding host rocks.

The formation environment typically involves:

• Oxidation of primary copper minerals

• Circulation of phosphate-bearing groundwater

• Low-temperature secondary mineral deposition

Cornish turquoise is considered rare due to the specific chemical conditions required for its formation. Specimens from documented localities such as Gunheath are highly sought after by collectors of British minerals.

Associated minerals in similar settings may include chrysocolla, malachite, opal and iron oxides, reflecting the complex supergene alteration processes of granite-hosted mineralisation.

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Physical Characteristics & Notable Traits

This Turquoise specimen may display:

• Rich blue to blue-green colouration

• Waxy surface lustre

• Massive or vein-like structure within matrix

• Natural colour zoning or subtle tonal variation

Cornish turquoise often occurs as nodular, vein-filling or massive material within decomposed granite or kaolinised host rock. Surface textures may range from smooth and compact to slightly porous depending on formation conditions.

Natural matrix attachment, subtle veining and mineral intergrowths are part of the specimen’s geological character and confirm authenticity.

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Geological Importance & Collectibility

Turquoise from Cornwall is significantly rarer than material from more widely known global sources. Specimens from the St Austell granite district represent a unique example of British secondary phosphate mineral formation linked to granite-hosted hydrothermal systems.

Collectors value Cornish turquoise for its documented locality, mining heritage and geological rarity. This specimen is suitable for mineral cabinets, regional British collections and educational displays highlighting phosphate mineralisation.

Because this is a genuine natural specimen, it displays unique structural and colour characteristics shaped by its geological environment. The photograph shows the exact specimen you will receive.

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Authenticity & Presentation

This Ultra Rare Turquoise specimen from Gunheath China Clay Mine has been carefully chosen for quality, colour and locality significance. Included with your purchase is a fully hand-signed Premium Certificate of Authenticity confirming its genuine origin from St Austell, Cornwall, England.

Combining classic Cornish granite geology with rare secondary phosphate mineralisation, this turquoise specimen offers documented provenance, regional geological importance and strong collector appeal in one carefully selected piece.