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Quartz
Hardness: 7 Streak: White
Environment: All environments
What to look for: Light-colored, translucent, very hard and abundant six-sided crystals, masses or veins in rock, or white, water-worn pebbles on beaches
Size: Quartz can be found in a large range of sizes, from tiny pea-sized crystals to fist-sized masses
Color: Colorless to white, brown to red; uncommonly purple
Occurrence: Very common
Notes: Quartz is the single most abundant mineral on earth, forming more than 12% of the earth’s crust, making it the most important mineral for collectors to study and be able to identify. Consisting entirely of silica, the silicon- and oxygen-bearing material that contributes to hundreds of minerals, quartz forms as distinct hexagonal (six-sided) crystals tipped with a point, often called “rock crystals.” Crystals are colorless to white when pure, but are often stained red, brown or yellow due to iron. Formations of quartz druse are common; quartz druse consists of layers of hundreds of tiny intergrown quartz crystals, often lining the insides of cavities, particularly vesicles (gas bubbles) in basalt or cavities in limestone. Massive formless quartz is very common and is often found as veins in cracks or rough masses loose in gravel, but quartz is most common as the most prominent mineral in rocks like granite and chert. Its hardness and crystal shape, if present, are its most diagnostic traits.
Where to Look: Quartz is literally found everywhere. Quartz druse can be found in basalt and rhyolite vesicles near Lake Superior, the rock of iron mine dumps near Tower, and cavities in the limestone of southeastern Minnesota. Lakeshore in northern Minnesota harbors much water-worn quartz.
