Zinnwaldite Mica | Trelavour Downs, St Dennis, Cornwall

An impressive 475g Zinnwaldite mica specimen from Trelavour Downs, near St Dennis in Cornwall's historic St Austell district. Featuring substantial overlapping mica formations, deep bronze-brown colouring and striking layered structures, this is a distinctive collector's piece showcasing the mineralogical diversity of Cornwall's granite landscapes.

Its dramatic, almost architectural appearance makes this specimen particularly appealing to collectors of British minerals, rare mica varieties and specimens associated with Cornwall's geological heritage.

Specimen Description

This substantial specimen displays an extraordinary arrangement of overlapping, plate-like mica formations, creating a naturally sculptural structure with pronounced ridges, folds and stepped surfaces.

The mineral exhibits a rich palette of bronze, smoky brown, dark chocolate and muted golden tones, with subtle metallic-looking reflections across the exposed cleavage surfaces.

Its most distinctive feature is the abundance of thick, intergrown mica plates. These display the characteristic sheet-like structure of mica minerals, with visible parallel layering and broad, reflective surfaces.

Several sections project outward at different angles, giving the specimen an unusually dramatic three-dimensional appearance. Smaller fractures and exposed edges reveal the intricate internal layering of the mineral.

Areas of pale cream and sandy-coloured material are visible on the reverse, contrasting with the darker mica-rich surfaces. These may represent associated host-rock minerals or weathered material, although their exact composition has not been independently identified.

The specimen retains its natural irregular edges, surface textures and mineral associations, making it a particularly interesting example of Cornish mica mineralisation.

About the Mineral | Zinnwaldite Mica

Zinnwaldite is the traditional mineralogical name used for a lithium- and iron-bearing mica associated with evolved granite and tin-bearing geological environments.

Modern mineral classification generally treats Zinnwaldite as a compositional variety within the siderophyllite-polylithionite mica series rather than as a separate mineral species.

Like other mica minerals, Zinnwaldite belongs to the phyllosilicate group, characterised by a layered crystal structure and excellent basal cleavage.

This structure allows mica to separate along parallel planes into thin sheets, producing the distinctive reflective, plate-like surfaces visible throughout this specimen.

Zinnwaldite is commonly associated with highly evolved granitic rocks, greisens and hydrothermal mineral systems, particularly those enriched in lithium, fluorine and tin.

Its colouring typically ranges from brown and bronze to darker grey-brown shades, depending on its chemical composition and the presence of iron.

The combination of pronounced mica layering and substantial intergrown plates makes this specimen especially attractive from a mineralogical perspective.

Trelavour Downs | Cornish Geological & Mining Heritage

This specimen is recorded as originating from Trelavour Downs, near St Dennis, within Cornwall's historic St Austell granite district.

Trelavour Downs is a particularly fascinating mineral locality, recognised for its lithium-bearing mica deposits and distinctive pegmatite geology. Unlike many Cornish mineral localities primarily associated with tin and copper extraction, Trelavour Downs has a history connected with the extraction of lithium-bearing mica.

Historically, mica from the Trelavour Downs Pegmatite was worked for use in firework manufacturing, providing an unusual connection between Cornwall's mineral resources and the pyrotechnics industry.

The locality is also notable for the exceptional size of some of its mica formations. Geological records describe mica crystals reaching approximately 15cm, demonstrating the remarkable mineral growth possible within this specialised geological environment.

The deposits occur within the wider St Austell granite district, formed approximately 280–300 million years ago during the late stages of the Variscan geological period.

As granitic magmas evolved, certain areas became enriched in elements including lithium and fluorine. These geological conditions contributed to the formation of specialised mineral assemblages, including lithium-bearing micas.

The wider St Austell region subsequently became internationally renowned for its china clay industry, which developed commercially from the eighteenth century onwards and transformed the surrounding landscape.

Today, the Trelavour area has renewed geological and industrial significance through modern interest in Cornwall's lithium resources, linking its historic mineral extraction with emerging battery-material industries.

This Zinnwaldite-labelled specimen offers a tangible connection to that remarkable geological story, from ancient granite formation and historic mica extraction to Cornwall's continuing importance as a source of critical minerals.

Provenance note: This specimen is supplied with Trelavour Downs, St Dennis, Cornwall as its recorded locality. The precise collecting point, extraction date and association with any individual historic working have not been independently established. Zinnwaldite is the supplied mineral identification and has not been laboratory verified.

Crystal Properties & Traditional Associations

Intention: Spiritual Growth, Calm & Protection

Within contemporary crystal practices, Zinnwaldite and other mica minerals are sometimes associated with emotional balance, reflection and personal transformation.

Their layered structure is symbolically connected with releasing old patterns, recognising personal growth and embracing change.

Brown and earthy-toned minerals are also traditionally associated with grounding, stability and maintaining a sense of calm during periods of uncertainty.

These associations are spiritual interpretations rather than scientifically established effects.

Associated Chakras

Root Chakra & Crown Chakra

The Root Chakra is traditionally associated with grounding, security and stability, while the Crown Chakra represents spiritual awareness and personal understanding.

Within symbolic crystal practices, Zinnwaldite may be used to represent a balance between practical stability and spiritual development.

Shape Symbolism | Natural Mica Formation

The layered formation of this specimen offers a beautiful symbolic representation of growth, transformation and the different experiences that shape us over time.

Its overlapping mineral plates can be interpreted as a reminder that personal development often happens gradually, layer by layer.

The specimen's dramatic natural structure also celebrates the extraordinary forms created by geological processes deep within the Earth.

Specimen Details

• Mineral: Zinnwaldite mica (traditional identification)
• Mineral Group: Mica, phyllosilicates
• Locality: Trelavour Downs, St Dennis, St Austell district, Cornwall, England
• Weight: 475g
• Dimensions: Approximately 92.8mm × 113.7mm
• Colour: Bronze-brown, smoky brown, dark grey and muted gold
• Formation: Natural overlapping and intergrown mica plates
• Finish: Raw, natural and unpolished
• Condition: Natural cleavage surfaces, irregular edges and associated matrix
• Quantity: One individual specimen
• Display Stand: Not included

You will receive the exact mineral specimen photographed. The display stand shown in the photographs is not included.

Mineral Care

Mica minerals have excellent cleavage and can separate into thin layers. Handle carefully and avoid pressure on exposed plates and delicate edges.

Keep the specimen dry and clean gently using a soft brush. Avoid soaking, abrasive cleaning methods and harsh chemicals.