Figure F17. Photomicrographs showing the nature of the pumiceous matrix in the pumice-lithic breccia and lithic breccia units. A. Pumice-rich matrix in the pumice lithic breccia, pumice clasts, and a few small lithic clasts. B. Pumice-rich matrix, a shattered K-feldspar crystal (left center), pumice clasts, and a basaltic lithic clast (lower right).