With the first piece, which most closely resembled the original stone, I covered it in white slip, then loosely brushed on cobalt oxide and underglaze colours, before finishing with a clear glaze. The result was colourful, but not very successful.
With the further 2 shapes, my 'apostrophes', I sratched into the sides of the shapes, highlighting these with copper oxide. I painted on a wax resist spiral before dipping into two glazes.
Fun to experiment, and has given me a new glaze combination (Copper red and Autumn shades) to use.