Yes, the zinc oxide in mineral makeup is the same white stuff that lifeguards use to keep their noses from burning to a crisp. But in mineral makeup, finely powdered zinc oxide provides the benefits of sun protection without the thick white paste. In addition to being a broad-spectrum sunscreen (it blocks both UVA and UVB rays), zinc is opaque, so it helps to conceal blemishes.
Like mica, zinc is non-irritating. It's also an anti-inflammatory, so it may even help to soothe red or itchy skin. (There's a reason it's used in diaper rash ointment!) Zinc is also used to thicken mineral makeup and help it adhere to the skin -- just like the next multi-tasking mineral on our list.