I have this rock that started out all white it had 1 thin black line in the center of it so me being curious I busted it in half with a sledge hammer well since I have busted it in half the small thin black line has slowly started like taking over the white part of the rock where i had hit it with the sledge hammer like it's bruising well today I came across it and I dropped it and almost before my very eyes it started bruising where i had dropped it . What kind of rock bruises is my question
Solano County California
Hi! You have a very odd rock. Minerals do oxidize but this is an interesting reaction because it is happening so fast. Since you didn't include a photo, I suggest you take it to a local geologist to have them help you out with the identification. Good luck!