What kinds of rocks make up the bedrock of Maine?
Taken as a whole, Maine’s bedrock comprises a vast array of rock types, some common and some rare, each with variations in mineral content, color, texture, and structure. Geologists classify rocks and assign them names based on certain basic characteristics, but the degree of natural variation is almost limitless. All three major rock groups – sedimentary, igneous, and metamorphic – are represented in Maine. Here is an abbreviated list of Maine rock types. Sedimentary rocks: shale, mudstone, siltstone, various sandstones, arkose, graywacke, chert, limestone, conglomerate. Igneous rocks (volcanic): basalt, andesite, dacite, rhyolite, various tuffs and breccias. Igneous rocks (plutonic): granite, pegmatite, quartz monzonite, syenite, diorite, diabase, gabbro. Metamorphic rocks: slate, phyllite, schist, granofels, various gneisses, marble, quartzite, greenstone, amphibolite, serpentinite, calc-silicate rocks, hornfels, migmatite, mylonite. For the distribution of rock types across Maine,
