Rocks & minerals Wisconsin, Illinois & Iowa : a field guide to the Badger, Prairie & Hawkeye states

Quartz Hardness: 7 Streak: White Environment: All environments What to look for: Light-colored, translucent, glassy and very hard six-sided crystals; also found as masses, veins, or river pebbles Size: Crystals can be up to several inches; masses can be any size Color: Colorless to white when pure; often stained yellow to brown, more rarely purple, dark gray, or reddish Occurrence: Very common Notes: Quartz is the most abundant mineral in the earth's crust and the first mineral all new collectors should study. It consists entirely of silica, the silicon- and oxygen-bearing compound that helps form hundreds of other minerals. Most abundant as a component of rocks, it often appears in uninteresting white masses in coarse-grained rocks such as granite or as the microscopic grains that make up chert (page 79). Nonetheless, crystals aren't rare and often appear as elongated hexagonal (six-sided) prisms ending in a point. Crusts or cavity-linings of many tiny intergrown quartz crystals are also common in the region; such crusts are called druzy quartz. White water-worn pebbles and chunky, coarse masses of quartz are found most anywhere, often buried in glacial till (gravel). All quartz is easy to identify, thanks to its distinctive high hardness, translucency, and conchoidal fracture (when struck, circular cracks appear). Where to Look: Quartz is found anywhere throughout the region, especially as worn pebbles. The Mississippi River cuts through areas rich with limestone that yield cavities and geodes lined with quartz. Look in southern Wisconsin near Prairie du Chien, in Iowa near Keokuk, and around Hamilton in Illinois. The Lake Superior shore and granite quarries near Wausau, Wisconsin, also produce fine crystals. Excerpted from Rocks and Minerals: A Field Guide to the Badger, Prairie and Hawkeye States by Dan Lynch All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.