Casting was pretty cool, it was all silver today. Only costs about $2 a gram to buy apparently. Gold is rather more exxy. They started last night by placing wax molds in steel cylinders which were then filled with a kind of heat-resistant plaster of Paris stuff and placed in a warmer overnight. By this morning, the plaster was as hard as a rock and the cylinders were inverted over a tray and the oven cranked right up, the wax quickly liquifying and running out through the hole in the block of plaster, leaving behind a perfect hollow imprint. Oven cranked up a bit more to actually burn out and destroy any bits of wax left in there. The cylinders are placed one at a time on their side in a kind of centrifuge. At the end of the centrifuge arm is a crucible made of some super heat-resistant porcelain which is heated with an oxy-acetylene torch until it is starting to glow and the silver lumps droped in. The silver quickly melts into a puddle and the cylinder with the plaster mold butts up against it. They yell "fire in the hole!!"

everyone stands back and the centrifuge is released, the spinning action forces the molten silver at high speed out of a little hole in the end of the crucible and down into the mold. When the spinning stops and things have cooled for a few moments, the cylinder containing the now-solid (but still red-hot) silver jewellery is removed and plunged into a container of water. It is then removed and the plaster carefully broken away - and there is the jewellery. Just needs a bit of cleaning and removing small metal bubbles and burrs.
I also progressed a bit further with that tiger eye cab. Still not at the polishing stage yet but have moved from the grinder to the flat disc - next one up will be a pre-polish. I have wet the stone in an attempt to demonstrate "chantoyancy" in still photos - the way the light moves across and through the stone as it is turned. Moonstone and a few other minerals also posses this quality.

Turn it another way, and the gold-copper coloured bands move and ripple across the stone, appearing to shift position.

Unfortunately, there are two major cracks in the stone that were not visible from the surface when I began shaping. I don't know if this is considered a major flaw or not - there are plenty of materials (emeralds for example) which are almost impossible to find without any cracks at all and it doesn't detract greatly from their value. I'm going to continue with this one, it was cut from a standard sized template so settings will be available that will suit perfectly. Not yet sure if I can cast one that will fit or if you have to cast first then cut the stone to size. It might be an actual silversmithing job - yet another thing to learn
