It begins with the chink of a pumice stone against flesh in the bath, followed by the discovery of glassy dust in her underwear.
One day she found a cluster of greenish-white crystals sprouting in her armpit. These she tried to prise away and failed. They were attached deep within; they could be felt to be stirring stony roots under the skin surface, pulling the muscles. Jagged flakes of silica and nodes of basalt pushed her breasts upward and flourished under the fall of flesh making her clothes crackle and rustle.
The protagonist’s initial horror gives way to a curious delight, and as her thoughts slow to stone speed and she becomes less mobile, she longs to find a place to stand outside in the weather.
Collected in Little Black Book of Stories, Chatto & Windus 2003. Also available online here