Glaze from locally-sourced materials

For potters must be close to the earth where their materials are; pots are of the earth and from the earth.

In his book Rock Glazes, published in 1983, Ivan Englund writes about finding and using local materials to make ceramic glazes. On page 18 he writes briefly about an igneous rock that we find on local beaches here in Australia: Pumice.

Pumice is a light porous rock caused by the frothing of the hot lava in contact with the sea. It floats around the oceans of the world and is often found on beaches. A great deal of the pumice on Australian Beaches came from the giant volcanic explosion of Mount Krakatoa in Indonesia around 1883. It is a basalt and can be used as a glaze material.