Cobaltian Calcite pseudomorph after Aragonite

Item Description

Every now and then, something surprises us even as jaded collectors who have seen tens of thousands of minerals, and you just sit back and say "what the heck is this" when looking at a new mineral. This is a very unique and artistic specimen, large as well, of pink Cobalt-bearing Calcite from Bou Azzer. However, the shape is all wrong for calcite! This piece is so unlike anything we have seen from here, with its divergent fans of long acicular, almost tube-like crystals of pink Calcite tinted by traces of cobalt to give its pastel pink color. Given the divergent sprays and the hollow character of the thin, straw-like "crystals" they may actually represent replacement of preexisting Aragonite by the Cobalt-bearing Calcite. We will therefore label this as a Calcite replacement of Aragonite. It is remotely possible that the replacement could be something else, but aragonite seems likely and the shape is wrong for a gypsum replacement as well. The largest sculptural fanspray that dominates the display face is 10.5 cm tall and 10 cm wide. If you look carefully at some of the individual "tubes" that are about 2 to 2.5 mm in diameter, most have hollow ends at their tips about 0.5 to 1 mm in diameter suggesting there was a slender, almost needle-like, pre existing mineral at the core, presumably of Aragonite, that was grown over then subsequently dissolved out. There are stouter, divergent sprays at the top left of the piece. Druses of pink Cobalt-bearing Calcite can be found lining the matrix of the piece in places. It is sparkling, geometric, big, and impactful. This was a key cabinet specimen on display in the home, in one of the choice major cases of Moroccan minerals of Erika Pohl's collection. She particularly loved this suite and the showcase was a thing of beauty, highlighted in part by the two large pink calcites shown here (another is also in this auction, of more traditional style).