First, you might like to know that sunblock is actually different from sunscreen. A sunblock physically blocks the sun’s UV radiation of the skin, both UVA and UVB. Like the way clothes, umbrella and trees work to shade us.
The most well-known chemical sunblock is zinc oxide and it scatters, reflects, and physically blocks UV radiation. Other commonly used sunblocks are talc, titanium dioxide, and red vetenary petrolatum.