Slate is a fine-grained, foliated, homogeneous, metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade, regional metamorphism. It is the finest-grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression.
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock containing 25% to 75% ash is described as tuffaceous. Tuff composed of sandy volcanic material can be referred to as volcanic sandstone.
Rhyolite is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly quartz, sanidine, and plagioclase. It is the extrusive equivalent of granite.
Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases, is an opaque, impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to iron(III) inclusions. Jasper breaks with a smooth surface and is used for ornamentation or as a gemstone. It can be highly polished and is used for items such as vases, seals, and snuff boxes. The density of jasper is typically 2.5 to 2.9 g/cm3. Jaspillite is a banded-iron-formation rock that often has distinctive bands of jasper.
Pumice, called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular volcanic rock that differs from pumice in having larger vesicles, thicker vesicle walls, and being dark colored and denser.
Travertine is a form of terrestrial limestone deposited around mineral springs, especially hot springs. It often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and rusty varieties. It is formed by a process of rapid precipitation of calcium carbonate, often at the mouth of a hot spring or in a limestone cave. In the latter, it can form stalactites, stalagmites, and other speleothems. It is frequently used in Italy and elsewhere as a building material. Similar deposits formed from ambient-temperature water are known as tufa.
A geode is a geological secondary formation within sedimentary and volcanic rocks. Geodes are hollow, vaguely spherical rocks, in which masses of mineral matter are secluded. The crystals are formed by the filling of vesicles in volcanic and subvolcanic rocks by minerals deposited from hydrothermal fluids; or by the dissolution of syn-genetic concretions and partial filling by the same or other minerals precipitated from water, groundwater, or hydrothermal fluids.
Petrified wood, also known as petrified tree, is the name given to a special type of fossilized wood, the fossilized remains of terrestrial vegetation. Petrifaction is the result of a tree or tree-like plants having been replaced by stone via a mineralization process that often includes permineralization and replacement. The organic materials making up cell walls have been replicated with minerals. In some instances, the original structure of the stem tissue may be partially retained. Unlike other plant fossils, which are typically impressions or compressions, petrified wood is a three-dimensional representation of the original organic material.
Scoria is a pyroclastic, highly vesicular, dark-colored volcanic rock formed by ejection from a volcano as a molten blob and cooled in the air to form discrete grains called clasts. It is typically dark in color, and basaltic or andesitic in composition. Scoria has relatively low density, as it is riddled with macroscopic ellipsoidal vesicles, but in contrast to pumice, scoria always has a specific gravity greater than 1 and sinks in water.
Bluestone is a cultural or commercial name for a number of dimension or building stone varieties, including:
Flagstone (flag) is a generic flat stone, sometimes cut in regular rectangular or square shape and usually used for paving slabs or walkways, patios, flooring, fences and roofing. It may be used for memorials, headstones, facades and other construction. The name derives from Middle English flagge meaning turf, perhaps from Old Norse flaga meaning slab or chip.
Dimension stone is natural stone or rock that has been selected and finished to specific sizes or shapes. Color, texture and pattern, and surface finish of the stone are also normal requirements. Another important selection criterion is durability: the time measure of the ability of dimension stone to endure and to maintain its essential and distinctive characteristics of strength, resistance to decay, and appearance.
Sentinel Peak is a 2,897 ft (900 m) peak in the Tucson Mountains southwest of downtown Tucson, Arizona, United States. The valley's first inhabitants grew crops at the mountain's base, along the Santa Cruz River. The name "Tucson" is derived from the O'odham Cuk Ṣon, meaning "[at the] base of the black [hill]". In the 1910s, University of Arizona students used local basalt rock to construct a 160 ft (50 m) tall block "A" on the mountain's east face, near its summit, giving the peak its other name, "A" Mountain. The peak is part of a 272-acre park, the largest natural resource park in the City of Tucson.
Jerusalem stone is a name applied to various types of pale limestone, dolomite and dolomitic limestone, common in and around Jerusalem that have been used in building since ancient times. One of these limestones, meleke, has been used in many of the region's most celebrated structures, including the Western Wall.
Fieldstone is a naturally occurring type of stone, which lies at or near the surface of the Earth. Fieldstone is a nuisance for farmers seeking to expand their land under cultivation, but at some point it began to be used as a construction material. Strictly speaking, it is stone collected from the surface of fields where it occurs naturally. Collections of fieldstones which have been removed from arable land or pasture to allow for more effective agriculture are called clearance cairns.
Oakley stone is the trade name of a building stone that occurs in the mountains of southern Idaho in the western United States. It is more properly known as Rocky Mountain quartzite or Idaho quartzite, a metamorphic rock. The stone is quarried south of the city of Oakley in Cassia County, northeast of the three-state border with Nevada and Utah. The quarries are located on the west slope of Middle Mountain in the Albion Mountains, northwest of the City of Rocks National Reserve.
Fall River granite is a Precambrian bedrock underlying the City of Fall River, Massachusetts and surrounding areas along the eastern shores of Narragansett Bay. It was formed 600 million years ago, as part of the Avalon terrane.
Brisbane tuff is a type of rock, formed as a result of a volcanic eruption. As the name suggests, it is a type of tuff found in Brisbane, Queensland, Australia. It is a form of welded ignimbrite. Brisbane tuff comes in a variety of colours: pink, green, blue (grey) and purple. The different colours are due to the extent of oxidation of iron and manganese.
The Playa de Las Canteras is the main urban beach of the city of Las Palmas de Gran Canaria, one of the most important beaches of the Canary Islands.
