amnhnyc: It’s time for #MineralMonday! In the late 1800s, gem-bearing pegmatites—like th
amnhnyc: It’s time for #MineralMonday! In the late 1800s, gem-bearing pegmatites—like this elbaite (variety: rubellite with quartz)—were discovered in Southern California. Pegmatites are a special kind of igneous rock characterized by large, occasionally enormous, interlocking crystals—sometimes of unusual minerals containing rare elements. Large crystals typically mean that magma cooled slowly, allowing crystals to grow for a long time, but pegmatites are rule-breakers—and are one of the most consistently puzzling aspects of geology. Special circumstances, particularly enrichment in H2O, allow them to solidify rapidly, sometimes in just a few days. Photo: E. Louis/ © AMNH #NewYorkRocks #crystals #gemsandminerals #amnh #naturalhistory #geology (at American Museum of Natural History)https://www.instagram.com/amnh/p/CXbwf9dvaha/?utm_medium=tumblr -- source link