Argillite is fine-grained clay particles that have been hardened by metamorphic processes (heat and pressure) and shows very little slaty cleavage (if it shows this cleavage it is referred to as shale). Both argillite and shale contain an abundance of clay particles, and both were formed in a deep-water environment, either fresh water lakes or marine. Weathering processes erode away rocks on the surface and sediment from these rocks is transported in streams and rivers to lakes or the ocean. The coarse particles settle out quickly along beaches, but very fine-grained clays and mud are carried into deep water where they settle and form mud on the bottom. Heat and pressure changes the mud to shale or argillite. These rocks can also contain fossils of plants and animals that once lived in the mud.
A dense, hard, finegrained, commonly feldspathic sandstone or siltstone of medium to dark or bluish-gray color that splits readily along original bedding planes to form thin slabs. Bluestone is not a technical geologic term. It is considered a variety of flagstone, with its thin relatively smooth-surfaced slabs suitable for use as flagging. The term has particularly been applied to sandstones of the Devonian age, quarried in eastern New York, Pennsylvania and in western New Jersey, but similar stones from elsewhere may carry the same name.
This is an extrusive igneous rock comprised of feldspars, quartz, and hornblende or biotite mica. It is chemically very similar to the granitic rock at the Graniterock AR Wilson Quarry, but because it was extruded by a volcano and cooled relatively quickly, it is much more fine grained. Rocks that are intrusive and cool slowly (over millions of years) can grow large crystals, like Graniterock AR Wilson granitic rock.
Limestone is formed in an undersea environment, chiefly by animals (such as coral and shellfish) absorbing calcium carbonate out of the ocean water and using it as their exoskeleton, or framework to support their body. Over time the animals become buried, and with pressure and time becomes limestone. In special “evaporative” ocean environments, like shallow lagoons, the calcium will form gypsum (calcium sulfate) instead of limestone, and the sea water become enriched in magnesium, which combines with the calcium carbonate to form dolomite. Dolomite can also form when ground water moving through the limestone replaces calcium with magnesium. Both limestone and dolomite can contain fossil material from the original sea animals.
Loose blocks separated from ledges by natural processes and scattered through or upon the groundcover regolith ("soil"); this name is also applied to similar transported materials, such as glacial boulders and cobblestones.
A coarse grained and generally igneous rock of even texture and light color, composed chiefly of quartz and feldspars. It usually contains small quantities of mica or hornblende, and sometimes minor accessory minerals. Depending on the feldspar present, granite may be pink, dark gray, or light gray. It is commonly believed to have solidified from molten rock (called magma) under pressure. However, some granite has no contact with surrounding wall rock, so it must have gradually degraded into metamorphic rock. Others show relic features found in sediments. This evidence suggests that some granite is not igneous in origin, but metamorphic. Some granite is the oldest known rock on earth. Crystallized at depth, granite masses are exposed at the earth’s surface by crustal movement or by the erosion of overlying rocks.
Jasper is an ornamental rock composed mostly of chalcedony (microcrystalline quartz) in association with other minerals, which give it colorful bands and patterns. It is opaque and colored red, yellow, brown, or off-white to gray. Jasper is usually formed by precipitation from superheated fluids, or quartz sand deposits that are subjected to tremendous heat and pressure. Jasper is usually found in association with agate and chalcedony. Jasper has long been used as an ornamental stone because it combines beauty and strength more perfectly than any other stone. Jasper is a type of quartz belonging to the chalcedony family, and along with its attractive colors, it has an inherent toughness (hardness 6.5 to 7.0) that makes it unique to any other stone produced in the world.
A sedimentary rock composed of calcium carbonate; includes many varieties, (oolitic limestone, dolomitic limestone, crystalline limestone.) Limestones that contain more than five percent magnesium carbonate may be termed calcite limestone, as distinguished from those that contain between five and forty percent magnes carbonate (magnesium or dolomitic limestone), and from those that contain in excess of forty percent as the mineral dolomite (dolostone, formerly known as the rock dolomited recrystallized limestones and compact, dense, relatively pure microcrystallin that are capable of taking polish are included in commercial marbles.
Marble is a limestone that has been crystallized by heat and pressure to a hardness that can be highly polished. Pure marble is white, but in various locations throughout the world, local impurities in the limestone host rock cause natural patterns and coloring that are distinctive and make each piece truly unique. Because of this, patterns and colors can vary with a flow and beauty only found in natural stone.
Quartz sandstone is a metamorphic sandstone consisting of quartz grains cemented with silica. It is not as hard as quartzite. Geologically, it is an intermediate rock between sandstone and quartzite. (See quartzite and sandstone pages for those specific definitions.)
Quartzite is a compact granular rock composed of quartz crystals, usually so firmly cemented as to make the mass homogeneous. The stone is generally quarried in stratified layers, the surfaces of which are unusually smooth, and therefore the crushing and tensile strength are extremely high. The color range is wide. In some deposits, because of the intrusion of minerals during the formation process, unusual shades of brown and gold are found.
River Rock is a natural rounded stone, with distinctive smoothness and colors. Centuries of moving glacial waters and shifting streambeds created this beautiful rock. Classic terrigenous sedimentary rocks consist of rock and mineral grains, or clasts, of varying size, ranging from clay-silt and sand up to pebbles and cobbles. These clasts were transported by gravity, mudflows, or running water, and eventually deposited in various settings in desert dunes, creek beds, streams and continental shelves. The term is also commonly used to describe paving stones, usually of granite composition. River Rock edging materials include ashlar and small building stones.
Sandstone is a sedimentary rock formed by the cementing together of grains of sand. The usual cementing material in sandstone iscalcium carbonate, quartz grains, iron oxides, or silica, and the hardness of sandstone varies according to the character of the cementing material. Quartz sandstone cemented with quartz is the hardest. Sandstone is durable and has a very high crushing and tensile strength.
Slate is a fine-grained rock formed when sedimentary rocks such as shale is meta-morphosed by great pressure. Slate splits into perfectly cleaved broad thin layers; this characteristically regular and planar cleavage is called slaty cleavage. In the formation of slate, pressure causes the flaky minerals within the sedimentary rock such as mica, clay, and chlorite, to be reoriented; the flat faces of the minerals lie at right angles to the source of the pressure, and the planes of easy cleavage are also at right angles to the source of the pressure. The rock is not necessarily compressed in the same direction as the sedimentary layers were originally laid down, and because the compression crumples and deforms the original sedimentary layers, the planes of slaty cleavage usually cut through the old bedding planes.
Travertine is a sedimentary calciferous stone formed in hot springs. Typically, hot water passes through limestone beds and takes the calcium from the limestone into suspension and takes that solution to the surface where the water evaporates and leaves the calcium crystals in layers on the surface. Travertine can be filled, usually with a cement filler or left unfilled for a more rustic appearance.
Water washed sandstone is a dense, hard, finegrained, commonly feldspathic sandstone or siltstone of medium to dark gray or bluish-gray color. It has naturally rounded edges, with distinctive smoothness and colors. Centuries of moving glacial waters and shifting streambeds created this beautiful rock. It was then transported by gravity, mudflows, or running water, and eventually deposited in various settings in desert dunes, creek beds, streams and continental shelves.