GEOLOGY AND MINERAL RESOURCES. A north east line drawn from Texarkana in the south western corner, through Little Rock to Pocahon tas in the northeast, divides the State into two parts; the northwest portion is underlain by Paleozoic rocks with a small area of Cretaceous rocks in its southernmost corner; the south eastern portion is occupied by the less consoli dated rocks of Tertiary and Post-Tertiary Ages. The Paleozoic area is essentially the 'hill coun try;' the Tertiary district is apart of the low level, fertile Atlantic coastal plain. The oldest rocks known in the State are of the Ordovician or Lower Silurian Age. They extend over the line from Missouri and lie on the southern flanks of the Ozark uplift, and consist of sandstones, quartzites, and limestones, the latter in the upper part of the series. They furnish good building stones, quartz sand for glassmaking, and lime. Along the southern boundary of the Ordovician formations, in the vicinity of Batesville and Cushman in Independence and Izard counties, are deposits of manganese ore which are worked to some extent, the product being shipped to steel manufacturers in the East. Another area of Ordovician rocks is found in the Ouachita :Moun tains west of Little Rock. In these mountains are large masses of a silicious rock, novaculite, from which are made the finest known whet stones, called in the markets "Arkansas" and "Ouachita" stones.
These whetstones are obtained in Garland, Howard, Hot Springs, Montgomery, Polk, Pulaski, and Saline counties, and their quarry ing constitutes an important industry. In con nection with the Ordovician rocks of the Ouachita uplift are found some deposits of manganese ore, but these are of little importance compared with those of the Batesville region. Around the edges of the Ordovician area of the northern part of the State is a narrow strip of Silurian limestone, the Saint Clair limestone, that furnishes a fine quality of pink marble useful for ornamental purposes. The Devonian formation is poorly
developed. It is known as the Eureka shale and the Sylamore sandstone, but is of importance for the reason that in connection with it are found phosphate deposits which give promise of yielding valuable returns. Gold and silver have been reported in large quantities in the Ouachita, Mountains, but examinations made by the State geologist have proven the reports to be erroneous or misleading, and the amount of these precious metals to be very small. Deposits of zinc blende have been opened recently in Sevier County, and other oceurrences of this ore, as well as of galena, are known in the northwestern part of the State. Aluminium ore in the form of bauxite occurs near Little Rock and farther west at Bryant in Salina County. Iron ores are of little impor tance, though they are found, at many places, in the form of limonite. Nickel is also known, but sparingly, in haling County. The coal measures cover large areas and furnish a good quality of bituminous coal in abundance. Oil and gas have been found only in small amount. In the Creta ceous and Tertiary areas nn metals have been found, but there are deposits of lignite and green sand.
Igneous rocks of great geologic interest are found at Magnet Cove and Fourche Mountain, in the eastern end of the novaculite region near Hot Springs. No Pre-Cumbrian known in the State. Mineral springs are common, espe cially so in the Ouachita Mountains. Those at Hot Springs are famous for their medicinal quali ties, and have led to the foundation there of a renowned health resort. The Ouachita Moun tains have been shown to be the westerly ex tension of the south end of the Appalachian moun tain system, and to have been formed at the same time and by the same causes that upheaved the Appalachians.