large Kutnohorite and Manganese-bearing Calcite

Item Description

Massive layered mushroom caps of earthy, fibrous, pink Kutnohorite which seems to be replaced by or mixed with Manganoan Calcite (the two form in a series of chemistry, and so this is not surprising). The top view shows 2 large 8.5 to 10 cm porous looking cauliflower growth habits. The side and underneath views show the sculptural multi-generational phases of growth of this rare manganese-rich carbonates. The calcite is fluorescent; and the kutnohorite should not be fluorescent - the shape is of kutnohorite, however even though it fluoresces! To our shocking surprise the Fluorescence shows the majority of this piece would be Manganoan Calcite So, we conclude this is a mixture with a little kutnohorite that constrained growth or more likely a pseudomorph, where the manganoan calcite has replaced the kutnohorite (in large part or full). The fibrous fans radiate out creating the initial layer after layer of stacked Kutnohorite and/or Manganoan Calcite. The piece is in excellent condition! There is some very minor contrasting black minerals, possibly Manganite, on the bottom. A much older piece from well known German collector Kurt Hefendehl's over 6000 piece worldwide collection. This piece has a catalogue number of SA-2, so his 2nd piece out of his 92 catalogued pieces from South Africa. It is a really beautiful pastel pink example of a Kalahari field classic, that is most likely a MN-Calcite replacement which kept the original form and structure of the first mineral, kutnohorite. Valued $2500.