Natural Prehnite · 27.13 ct · Octagon · Africa · Unheated

This substantial natural Prehnite weighs an impressive 27.13 carats and is fashioned in a large octagonal mixed cut, combining considerable gemstone volume with a geometric presentation that provides an extensive view of its distinctive internal structure.

Measuring approximately 20.0 × 17.2 × 10.7 mm, the gemstone has an exceptionally strong face-up presence. Its broad proportions and considerable depth make the specimen particularly suitable as a statement gemstone, collector piece or centre stone for an individually designed jewellery setting.

The material displays an attractive yellowish-green body colour with a translucent appearance. Within the Prehnite are prominent black Epidote needle inclusions, producing a striking natural contrast and giving the gemstone an immediately recognisable individual character.

Prehnite is a calcium-aluminium silicate mineral belonging to the phyllosilicate group. Gem-quality material is commonly encountered in pale green, yellowish green and related tones, with transparency ranging from translucent to occasionally near-transparent material.

The internal character of this specimen is particularly important. Its clarity is comparable to an I3 profile, with abundant and readily visible inclusions throughout the stone. The dark Epidote needles, together with associated natural growth features and internal structural variations, significantly influence transparency and optical performance but simultaneously form one of the principal aesthetic features of the gemstone.

Rather than presenting the highly clean appearance sought in many transparent faceted gemstones, this Prehnite derives much of its individuality from the relationship between its soft yellowish-green host material and the strongly contrasting mineral inclusions.

The large octagonal mixed cut has been used effectively to expose this internal mineral architecture. The broad table and geometric outline provide a clear view into the included material, while the mixed faceting contributes surface reflection and additional visual depth.

The gemstone has a Good cut grade, with Good symmetry and Good polish. Its surface displays a Fair to Good vitreous luster, supporting an attractive overall finish while retaining the softer optical character associated with translucent Prehnite.

This specimen is recorded as originating from Africa and as unheated, with its colour and internal mineral features presented in their naturally observed state.

With its impressive 27.13 ct weight, soft yellowish-green colour and dramatic network of natural black Epidote inclusions, this Prehnite is a highly individual gemstone. Its substantial dimensions and distinctive internal mineral structure make it particularly appealing for collectors or for a bold custom jewellery design in which the natural inclusions can remain the visual focus.