Vivianite

An excellent and distinctive example of vivianite from Raglan, Waikato District, New Zealand. The specimen consists of a dense group of intergrown, rounded vivianite nodules, each composed of tightly packed, radiating bladed to acicular crystals. Where the nodules are partially open, their internal radial structure can be clearly seen. The vivianite is a very dark greenish-blue to nearly black in normal lighting, with occasional crystal faces catching the light with a bright vitreous lustre. Portions of the surface carry a thin rusty-brown coating, likely goethite or other secondary iron oxides.

Vivianite from the Raglan area occurs in an unusual nodular habit quite unlike the large individual crystals for which the species is perhaps better known. These nodules formed within sedimentary material, with the rounded aggregates composed internally of fine radiating vivianite crystals. An interesting and highly characteristic New Zealand occurrence of vivianite, and an excellent example of the unusual habits this iron phosphate can assume.