Zinc Oxide is a white powdered mineral that is found in our environment, but not in huge quantities. All zinc oxide in cosmetics is synthesized in a lab, faithfully mimicking the structure and properties of the naturally occurring stuff.
Testing has proven its ability to soothe inflamed skin and act as a broad-spectrum sunblock, as well as having antibacterial properties and providing a barrier for the skin.
Fun fact: Zinc Oxide is NOT reef safe, despite several brands claiming it is and has been definitively linked to coral bleaching.
Zinc oxide has many many years of safe use behind it, and the only safety issued associated is with inhaling large quantities over time- something that will not occur with the use of Ethique products.