File:Bulletin 426 Plate XXII A Rion Quarry.jpg
The granites of Fairfield County, especially those of the Rion and Anderson quarries of the Winnsboro Granite Corporation, are probably the South Carolina granites best known beyond the limits of the State. They are mica granites but show variation in color and texture and are naturally grouped commercially into those most desirable for (a) building stone and (b) monumental stock. The product from the Rion quarry (gray granite) is used chiefly as a building stone; that from the Anderson quarry (blue-gray granite) is used exclusively for monuments. These two quarries were the only ones operating in Fairfield County at the time of examination in July, 1908.
The Rion quarry is located at Rion, 5 1/2 miles southwest of Winsboro, and is connected by a standard-gage spur track with Rockton, a station on the Columbia, Spartanburg and Asheville division of the Southern Railway 4 1/2 miles to the east. (See Pl. XXII, A.)
The rock is a biotite granite of light-gray color and medium grain. Its minerals are potash feldspar (orthoclase, in large part intergrown with plagioclase as microperthite, and microcline), soda-lime feldspar (oligoclase), quartz, and biotite, together with accessory apatite, zircon, and iron oxide and secondary chlorite, epidote, and colorless mica. Intergrowths of feldspar (microperthite) and of feldspar and quartz (micropegmatite) are abundant. The potash feldspar shows Carlsbad twinning. Inclosures of irregular rounded quartz, feldspar, and quartz-feldspar intergrowths (micropegmatite) are numerous in the larger feldspar individuals. The soda-lime feldspar shows more alteration than the potash varieties, chiefly into kaolin and colorless mica.
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The quarry was opened about 1883, but systematic quarrying did not begin until fifteen years later. The quarry face is 300 feet long and 20 feet deep. (See Pl. XXII, B.) There is no stripping in the direction of working of the present quarry face. In other places the granite is decayed to a depth of 3 to 6 feet.