Talcum is a soft, smooth powder made from a mineral called talc, which is one of the softest minerals on Earth. You can crush talc between your fingers, and it feels slippery and silky.

People have used talcum powder for over a century to keep skin dry and prevent chafing (irritation from skin rubbing together). Parents often sprinkled it on babies after baths, and athletes used it to keep their feet dry. The powder absorbs moisture, which is why gymnasts dust their hands with powdered talc before gripping the parallel bars, and rock climbers use it on their fingers for a better grip.

The mineral talc itself forms deep underground when certain rocks are exposed to heat and pressure. It's so soft that scientists use it as the number 1 reference point on the Mohs scale, which measures mineral hardness from 1 to 10. Diamond, the hardest natural material, rates a 10, while talc sits at the opposite end.

Talcum powder usually appears pure white and has almost no smell, though companies sometimes add fragrances. While it was once very common in bathrooms everywhere, doctors today recommend other products for babies because talcum powder can irritate babies' lungs if they breathe it in.