Rhodusite is magnesio-reibeckite, a beautiful blue amphibole mineral. The fibrous crystals are naturally stabilized with microcrystalline quartz. The long axis of this crystal is chatoyant, similar to pietersite.
This is a rare mineral found only in a couple of places around the world. The names comes from the Island of Rhodes off the coast of Greece.
This material tends to want to split along the crystal axes. In order to minimize this I put a temporary back on the slab, cut and polish the top and then remove the back. You can glue it on with a glue that can be removed with acetone or alcohol or you can cut the back off.