What is Slate?
Slate is a metamorphic rock exhibiting “slaty” cleavage, which allows it to be split in thin sheets. Slate is formed in the water of rivers and ponds from clay accumulating in thin, flat layers at the bottom of these waterbeds. Slates are softer than granite and therefore vulnerable to scratching and abrasion. Slate has a natural cleft (not a smooth surface). The same precautions mentioned for marbles with regard to damage should be applied to slates.