Diamond Apophyllite Cluster on Chalcedony — High Lustre Terminations with Botryoidal Matrix

Diamond Apophyllite Cluster on Chalcedony — High Lustre Terminations with Botryoidal Matrix

This Apophyllite cluster is a bold, multi-layered display specimen, featuring sharply defined “diamond” terminations set across a dark, textured chalcedony matrix.

The apophyllite crystals exhibit strong vitreous lustre with a mix of transparent to slightly milky clarity. Multiple well-formed terminations reflect light cleanly, creating bright flashes across the surface. Some crystal faces show natural growth striations and internal veils, adding depth and confirming natural formation.

The base is composed of chalcedony with a botryoidal (rounded, clustered) structure, visible as the darker, grape-like formation beneath the crystal growth. This creates a clear contrast between the smooth microcrystalline base and the larger, well-defined apophyllite crystals.

Across the surface, there are areas of fine druzy crystallisation and mineral inclusions, contributing additional sparkle and texture throughout the piece.

Key Features

• Material: Apophyllite on Chalcedony

• Chemical Composition:

  - Apophyllite: KCa₄Si₈O₂₀(F,OH)·8H₂O

  - Chalcedony: SiO₂

• Colour: Clear to pale apophyllite with dark grey/green chalcedony base

• Crystal Habit: Tetragonal prismatic crystals with pyramidal terminations

• Formation: Secondary mineral growth within volcanic cavities

• Transparency: Transparent to translucent

• Lustre: Vitreous (glass-like)

• Feature Highlights:

  - Multiple high-lustre “diamond” terminations

  - Botryoidal chalcedony matrix

  - Druzy crystallisation across base

  - Internal inclusions and natural veils

  - Layered, multi-stage mineral growth

Dimensions

• Size: 7 cm x 5.5 cm

• Weight: 145 grams

Geological & Scientific Notes

Apophyllite forms in basaltic volcanic environments, typically within gas cavities where mineral-rich fluids deposit crystals over time. The well-defined tetragonal crystal habit seen here is characteristic of stable growth conditions within these cavities.

The chalcedony base formed earlier, as silica-rich solutions deposited microcrystalline quartz in rounded, botryoidal layers. This stage created the foundation for later mineral growth.

Apophyllite crystallised afterwards, growing outward from the cavity walls and over the chalcedony surface. This sequence results in the distinct contrast between the smooth, rounded base and the sharp, reflective crystal terminations.

The “diamond” appearance is due to the combination of crystal geometry and high surface reflectivity, which maximises light interaction across the faces.

Druzy areas and fine crystal coatings indicate continued mineral activity after the main crystal growth phase, adding texture and sparkle to the specimen.

Condition

• Multiple intact crystal terminations

• Strong overall structure with stable base

• Natural inclusions and surface features present

• Minor edge contacts consistent with natural growth

• No repairs or artificial enhancement observed

Care Instructions

• Handle with care — apophyllite is relatively soft (Mohs ~4.5–5)

• Avoid knocks to crystal points

• Clean gently with a soft brush or dry cloth

• Avoid prolonged water exposure

• Store separately to protect terminations