Quick answer: Banded iron formations are layered rocks of alternating iron oxide (hematite or magnetite) and chert, mostly formed between
Banded Iron Formations: The Rocks the Great Oxidation Event Left Behind Read Post »
Quick answer: Exsolution is when a crystal that formed as one uniform mineral at high temperature separates into two minerals
Exsolution: When One Crystal Splits Into Two From the Inside Read Post »
Quick answer: Most meteorites are unusually heavy for their size, attract a magnet (because they contain iron-nickel metal), have a
Meteorites: How to Tell a Space Rock From a Hot Rock Read Post »
Quick answer: Chalcedony is quartz made of crystals too small to see without a microscope: fine fibers packed together. Agate
Agate and Chalcedony: Quartz You Cannot See the Crystals Of Read Post »
Quick answer: A stalactite grows when water seeping through limestone enters a cave, releases carbon dioxide into the cave air,
Quick answer: “Gem quality” means a stone is transparent or attractive enough, free enough of cracks and inclusions, and durable
Quick answer: Schorl is the black, iron-rich member of the tourmaline group and makes up the vast majority of all
Schorl: The Black Tourmaline Hiding in Half the World’s Granite Read Post »
Quick answer: Amethyst fades in sunlight because its purple color comes from color centers: iron atoms in the quartz altered
Quick answer: Feldspar is the most abundant mineral group in Earth’s crust, making up roughly half of it. The group
Feldspar: The Most Common Mineral on Earth, and Nobody Collects It Read Post »
Quick answer: Calcite forms three classic crystal shapes: dogtooth (pointed scalenohedrons that look like canine teeth), nailhead (flat-topped crystals shaped
Dogtooth, Nailhead, and Rhomb: Calcite’s Three Famous Shapes Read Post »
