thanks for your responses but they have both only appeared as private messages, not on the main BCN page ??
anyway the material seems too dense and hard for organic material unless it were a very hard nutshell -and the broken one is the same colour at the broken edges - the range of colours does remind me of soapstone.
it doesn't help that the vendor repeated what someone had told him
that they were so very ancient, and someone suggested it was Lava stone...