Excerpt from The Mineralogy of the Chicago Area Although its rocks enclose no stores of precious metals or minerals used as gems or for ornamental work, and although lists of mineral localities do not mention Cook County, still the number of minerals that are found is great enough to ac complish several desirable results. First, they represent five out of the eight great groups or classes into which the mineral world is divided; second, they illustrate the chemical, crystal lographic, optic, and other physical properties of minerals; third, they demonstrate the chief methods of investigation; fourth, some of them are of such occurrence as to make contribution to the science of Mineralogy. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.