|In 1576, while invading South America, the Spanish army seized a large iron meteorite referred to as “Field of the Sky” in local legend. The discovery of fragments of the meteorite continues.
||Vapor pockets sometimes form in cooling granite magma; crystals grow inside these hollows, forming what are called druses.
||Opal’s beautiful color is not the material color of its crystals. The color you see arises from light refracting in delicately arranged crystal particles. The mineral is relatively soft because of the presence of water molecules.
||Geologists often use “index fossils” to determine the age of stratum. Uncovering a species whose time period is known, scientists can identify when the surrounding stratum formed. Because of their morphologic distinctiveness, common occurrence, a broad, worldwide geographic range, and a narrow or restricted stratigraphic range, trilobite species are very useful as index fossils.