Denise: In High Field there’s an outcrop of partially metamorphosed granite with prolific inclusions (both veins and lumps) of biotite – a type of mica that’s black, soft and very flaky. The large crystals of the granite are ‘granulating’ from the effects of weather, and doing so unusually easily, such that the parent rock is actually eroding faster than the biotite, which as a result stands out like varicose veins, or chocolate chips in a cereal bar. How ironic, one of the weakest of minerals proving more durable than what is normally one of the strongest of rocks!
J brought this to my notice when he came home with a heart-shaped lump obviously from the boundary between the biotite and the parent granite, with one side micaceous, the other side fine crystalline dark granite. It takes a man with a heart of stone to win over a female geologist!