What was the lava from Mt St Helen's made out of when it erupted in 1980?

The material erupted in the 1980 eruption of Mount St Helens was of a composition known as dacite. Minerals common in dacite are primarily quartz, potassium feldspar, and albite. However most of the dacite from the 1980 eruption came out as ash and pumice, which are varieties of volcanic glass. Although the chemical components were there, the material cooled to quickly for the minerals to form.