The Rockmart Geological Formation
The Rockmart Slate is a unique rock unit in the northern Georgia Valley and Ridge Province. Economically speaking, mining of the Rockmart for roofing slate started back in the early1800’s. Later, the slate was mined for lightweight aggregate and today, it is quarried for mostly crushed and broken stone that has a variety of industrial uses. The Rockmart Slate has a basal contact with the Newala Limestone, which is actively mined in the area of the Rockmart Slate Company Quarry for high-calcium and aggregate limestone. Historically, the geologic origin of the Rockmart Slate has been the topic of debate. Both the upper and lower contacts of the unit have been argued to be either, or both, unconformities or faults (see Cressler, 1970, and more recently, Kathet all., 2008 and Tull and Hilton, 2008).
One reason for confusion over the nature of the contacts stems from the fact that the Rockmart is a slate, which is a type of metamorphic rock (that is, changed from a sedimentary shale due to actions of heat, pressure, and chemically active fluids deep within the Earth, in this case when the Appalachian Mountains formed hundreds of millions of years ago.), and it remains a mystery how it became sandwiched between sedimentary rock layers that are not metamorphosed.
Finally, the present-day geologic setting of the Rockmart Slate is also unexplained. It lies at the center of a huge bend in the Appalachian Mountain Chain, known as the Cartersville Reentrant (a reentrant is a bend that is concave away from the average trend of the mountain belt). How the reentrant formed remains a mystery, but the result is that the Rockmart occurs well east of the frontal Appalachians, providing an unparalleled glimpse of how the ancient margin of proto-North America (Laurentia) looked just prior to its Appalachian destruction
What is Slate?
Slate is a general descriptive term for dense clayey or shaley rock of such fine texture, that the individual grains or crystals cannot be seen without magnification, and which has cleavage that causes it to break into thin platy fragments. Slate has formed by heat and pressure deep within the earth’s crust, by a process known as metamorphism.
There aremany forms and types of slate, with varying market applications and values. Uses for slate can be generally divided into those for which aesthetic appearance is most important, and those for which it’s value is based on it’s strength and bulk density as a concrete aggregate.
Those applications of slate in which aesthetic appearance is key to market acceptance include split stone for architectural and landscaping uses. Prices per ton are quite high in this market, but tonnage volumes are low. Long term success in this segment of the lsate business is tied to architect’s, landscape gardener’s and consumer’s fashion trends in natural and synthetic products. For some years now, natural stone of irregular sizes, shapes and surface textures has been well accepted and is in considerable demand.
The Rockmart Slate is a distinctive rock formation named for characteristic outcrops near Rockmart, Georgia by Haynes(1891)It is known to extend (Butts, 1948) from tow miles southeast of Taylorsville in Bartow County nearly to the Alabama Border, near Eson Hill in Polk County; a distance of approximately 20 miles.
Outcrops and occurrences of Rockmart Slate are abundant throughout this area. As Rockmart Slate is strongly cleaved and breaks into splintery fragments, it becomes indistinguishable from phyllites and schists in the immediate vicinity of the Cartersville (Emerson Fault in extreme southern Polk County.
There have been various estimates of the thickness of the Rockmart Slate. Butts (1948) states that “No certainly recognized beds or horizons have as yet been detected, that would serve aas datum planes for measurement. Various estimates have been made ranging from 1,200 to 3,000 feet. In the writer’s judgment 3,000 feet is not excessive; it may be much thicker. Higgins (1988), however, reports that Rockmart is a “relatively thin (about180 meters, 560 feet) sequence of slate and siltstone.” Whatever the actual thickness of the Rockmart Slate formation, it is clear from the abundance of outcrops, that the dark slate is a very plentiful mineral resource on the subject property and in the general area.
E-mail: info@rockmartslate.com
Located in the heart of the Coosa Valley area of Northwest Georgia, Rockmart is situated in a triangle formed by Atlanta, Georgia; Birmingham, Alabama; and Chattanooga, Tennessee. The name was derived from Rock Market because of it’s abundance of slate, limestone, iron shale, and clay.
Back in the days of the Civil War and for some years after, the leading town in East Polk County was little Van Wert which was settled by Welsh miners in 1838. They worked in the slate and rock quarries of the area.
When the first railway was being built, Van Wert was immediately thought of as the logical place for the Southern Railway depot to be built. However, a wealthy landowner, Colonel Seaborn Jones, offered land and money for a station to be built one mile west of Van Wert, in an area that became Rockmart, which was incorporated in 1872.
