(Swedish: "rock flint"), white, gray, yellow, greenish, or pink fine-grained rock that consists of quartz intimately mixed with feldspar. It is very finely crystalline, resembling the matrix of many silica-rich (acid) igneous rocks. Many examples are banded or striated; others contain larger crystals of quartz in a fine-grained matrix. Mica, iron oxides, apatite, zircon, epidote, and hornblende may be present in small amounts.
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