Geibikei, Higashiyama, Higashiiwai, Iwate, Japan

This river sand is medium-sized (about 0.3mm in diameter) mixed with coarse sand.  The grains are moderately sorted.  It consists of quartz and feldspar.  The grains are angular.  It is mixed with a lot of coarse flakes of biotite (2.0mm diameter or less).