A shipment of large Moroccan crinoids of the species Scyphocrinites elegans just arrived yesterday. Crinoids are filter feeding sea animals (not plants) which attached themselves to the bottom of the ocean with a stalk. They are echinoderms related to starfish, sea urchins, and brittle stars.
The highly detailed Scyphocrinites crinoids are Upper Silurian in age (420 million years old) and are mined near Boutschrafin, Erfoud, Morocco. To reach the crinoid layer the workers must dig deep vertical shafts, sometimes 30 feet in depth. They then tunnel horizontally along this layer to extract plates of crinoids. These plates must then be brought up to the surface in small pieces using a bucket where they prepared. One can only imagine that is back-breaking, hot and dangerous work.
The crinoids plates are then reassembed on the surface, and typically prepared using chemical methods. Below are photos of the preparation. I'm not totally sure but I believe the chemical being used is Potassium hydroxide. It's a very strong base (opposite of acid) and will disolve the surrounding rock without damaging the crinoids fossils which are calcite based. This is actually a very tedius process that takes weeks to complete. Small bits of solid potassium hydroxide must be applied and left to disolve before more can be applied. It has to be done carefully so no too much rock is removed causing the fossil to fall apart.
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