Slate

Pacific Black Slate is a fine-grained, metamorphic rock that is formed from shale or mudstone through low-grade regional metamorphism. It's known for its ability to be split into thin, durable layers or sheets, a property called fissility. Slate forms under relatively low temperature and pressure conditions compared to other metamorphic rocks. Over time, sedimentary shale is compressed and heated, causing its minerals to realign and form a denser rock with the typical slate cleavage. It’s used for pavers, copings, pier caps, walls,  risers, curbs, cobbles and many other applications.