At Anthracite, near Crested Butte, high-grade anthracite coal was mined for a time. Identical in origin with other Colorado coal, the anthracite of this region was hardened by heat and pressures from Tertiary igneous intrusions forcing their way into local sedimentary rocks during post-Cretaceous mountain building. A multitude of other coal camps are scattered about Colorado: Cokedale, Delcarbon, Coaldale, Roncarbo, Carbondale, and Cardiff stand out because of their suggestive names. These early small camps are, like their metal-mine cousins, largely deserted today. CONSTRUCTION MATERIALS Sand, Gravel, and Clay Sand, gravel, and crushed rock rate high among geologic products in Colorado; more than $27,000,000 worth of these materials were produced in the state in 1969. Highway and construction activities have brought recent expansion in the number and size of quarries and gravel pits. Increasingly, Coloradoans are insisting that quarries and pits be excavated only where they will not mar the natural beauty of the landscape, and many old pits are now being filled in. Unfortunately, the scars left by some quarries—such as that on the Rampart Range near Colorado Springs—are difficult to erase. Clay of good quality occurs in Cretaceous deposits in many parts of Colorado, most frequently in the Dakota or Laramie Formations. In the area around Golden, the Coors Porcelain Company for many years mined clay for use in pottery and low temperature ceramic ware. Scars from this mining can be seen along the mountain front north and south of Golden, and deep clefts within the town, just west of Colorado School of Mines, testify to the amounts of clay that have been removed. Colorado clay is not pure enough to be used in high temperature ceramics, and the present use for it is in the manufacture of common tiles and bricks. A recent development in Colorado is the use of Cretaceous Pierre shales in manufacturing lightweight aggregate for building. The shale is mined between Golden and Boulder, near Colorado highway 93. In the nearby plant, it is pulverized and then heated in a large rotating cylinder until the surface of each particle fuses. Then the particles are quickly cooled. The resulting product is much like cinder, light in weight and yet strong. It can be mixed with cement for use in construction work requiring a great strength-to-weight ratio, or made into concrete blocks. [Illustration: Quarrying of Paleozoic limestones and dolomites along the east flank of the Rampart Range northwest of Colorado Springs has badly defaced a prominent mountain backdrop. Recent seeding efforts by quarry operators are returning the exhausted part of the quarry to its original lightly vegetated condition, and hopefully, as the quarry is depleted, the scar will disappear. (John Chronic photo)] Stone