Cobaltoan Calcite with Manganese Oxides

Description

A vivid pink crystalline area and scattered dark manganese oxides contrast with the pale, substantial natural matrix.

This compact Kolwezi specimen displays sparkling pink Cobaltoan Calcite across one side of a pale natural matrix. Small black manganese oxide areas punctuate the crystalline surface, while the broad cream-coloured portion shows its solid three-dimensional form. The photographs capture the exact piece from several angles.

Cobaltoan Calcite owes its characteristic pink colour to cobalt incorporated within the Calcite structure. This specimen offers a clear contrast between that pink growth, dark associated oxides and its lighter host material.

Locality: Kolwezi Mining District, Lualaba Province, Democratic Republic of the Congo.

Condition and photography: Natural surface irregularities and contacts are visible. Colour can vary with lighting and screen settings. Handle from the matrix and keep away from acids.

Calcite is calcium carbonate, a mineral with an unusually wide range of crystal forms. It occurs in sedimentary rocks, mineral veins and many other geological settings. Although the composition remains broadly the same, differences in growth conditions can produce dramatically different outlines, from broad faces to slender or densely grouped crystals. This variety is part of its interest for a mineral collection.

Calcite has well-developed cleavage: it can split along particular planes in its crystal structure. Its natural growth faces and cleavage surfaces therefore deserve careful distinction. Transparent, translucent and more opaque examples all occur. The shape, arrangement and surface character of this piece are more informative than colour alone, especially when comparing specimens from different localities.

The recorded origin is Kolwezi Mining District, Lualaba Province, DR Congo. Within a collection of Calcite specimens, this locality gives the piece a geographical identity alongside its particular crystal habit and natural setting.

The specimen measures 60 × 40 × 40 mm, with a recorded weight of 200 g. The proportions give a useful guide to its place in a display, with the individual crystal arrangement and mineral association remaining the principal points of interest.

Calcite is relatively soft and has pronounced cleavage, so support the stable part of the specimen when moving it. Avoid pressure on thin plates or projecting points. A secure display helps preserve the delicate edges and the arrangement of growth described for this piece.