alandhart

Just imagine it! In March 2003 a huge cavity was broken into at the Navegadora mine, Conselheiro Pena, Minas Gerais, Brazil. The cavity was 10x10x3 metres (!) and contained several tons of large quartz and albite collapsed into the pocket. However, the most interesting part was the approx. 100kg of spessartine garnet crystals, up to 10cm on edge with peculiar ‘etching’ and a bright burgundy-red colour. This one from Marco Tironi is a perfect example and how bizarre they are? Seemingly here a ‘dodecahedron’ with slight irregular shape, clean and completely crystallized with distinctive complex stepped faces that were a signature of this find - still the only one that produced these amazing crystals. With great colour and luster, I love the way the ‘sun’ gives an almost chatoyant effect or reflection from the face ‘forms’ as I turn it. There has been some debate as to how these crystals form and whether they grew like this or where ‘etched’ post crystallization. Analysis shows the crystals are homogenous in chemistry from core to rim, hinting that there was not any later stage crystallization from evolved fluids, a feature often seen in pegmatite minerals being ‘zoned’, and the thought is that the final ‘fluid’ was at equilibrium with the ‘contents’ and the overall morphology has arisen from etching, even though this ‘gross reticulation’ by etching is superbly clean! Great specimen and from a now classic locality easily identifiable 👍🏻

(Source: instagram.com)