Selenite (mineral) was filled with mineral-rich water that drove the crystals' growth. The largest of those crystals weighs 55 tons, is long, and is over 500,000 years old. Gypsum occurs on every continent and is the most common of all the sulfate minerals. Gypsum is formed as an evaporative mineral, frequently found in alkaline lake muds, clay beds, evaporated seas, salt flats, salt springs, and caves. It is frequently found in conjunction with other minerals such as, copper ores, sulfur and sulfides, silver, iron ores, coal, calcite, dolomite, limestone, and opal. Gypsum has been dated to almost every geologic age since the
Arctic vegetation Arctic vegetation In the Arctic, the low tundra vegetation clothes a landscape of wide vistas, lit by the low-angle light characteristic of high latitudes. Much of the Arctic shows little impact from human activities, making it one of the few places on earth one can see intact ecosystems. Arctic plants are adapted to short, cold growing seasons. They have the ability to withstand extremely cold temperatures in the winter (winter hardiness), but what is even more important is the ability to be able to function in limiting summer conditions. Arctic plants have a compressed growing season; they initiate growth rapidly