Calcite with Natrolite

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Although not bright and colourful, there is a certain intrigue and fascination to this unusual form of Calcite from Stríbro (Mies) in the Plzen Region, Bohemia, Czechia. Cabinet-sized, this aggregate of Calcite crystals encases a core of massive dark brown Sphalerite. Growing outwards, the Calcite crystals have consistently developed in a crown-like, or castellated form, with their sunken internal part dull and pale grey, whilst the outer raised edges are more glossy to resinous in lustre. This formation appears to have resulted from several generations of crystallization, with the later, glossy, outer edges containing fine inclusions of golden Pyrite. Minor small prismatic crystals of Natrolite are sparse, but focused more upon the rough surfaces of the earlier 'internal' Calcite crystals. Ex Hans Engelbrecht Collection (no. 379) with his card label. There is minor bruising to some of the external Calcite crystals and one or two of the higher display crystals, but this is a rarely seen variety and thus an important specimen.