brownstone, red to brown variety of sandstone. Its unusual color is caused in some instances by the presence of red iron oxide which acts as a cement, binding the sand grains together. Vast thicknesses (up to 20,000 ft/6,096 m) of brownstone were deposited in the present-day Connecticut River Valley of Massachusetts and Connecticut and in central New Jersey during the latter part of the Triassic period. Quarries in these regions were the source for much of the building stone used in the late 19th and early 20th cent. in the construction of the many brownstone houses found from Baltimore to Boston; the stone, however, is not very durable, especially if poorly laid or maintained. Similar, but more brightly colored, sandstones also were deposited in the Rocky Mt. region during the Triassic period and Jurassic period. These deposits are called "redbeds" and make up the colorful landscapes of the Painted Desert of Arizona.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.