144 articles
Kimberlite
Kimberlite, also known as blue ground, is an ultramafic volcanic rock occurring in vertical pipes, named after Kimberley, South Africa, and the primary source of diamonds.
Lamproite
Lamproite is a rare ultrapotassic alkaline igneous rock derived from metasomatized lithospheric mantle, one of two rock types hosting economic primary diamonds, recognized after the Argyle discovery in 1979.
Large igneous province
A large igneous province (LIP) is a vast accumulation of mostly mafic igneous rock covering over 0.1 million km², emplaced over less than 50 million years.
Latite
Latite is a volcanic rock made of roughly equal alkali feldspar and sodic plagioclase with little or no quartz, making it the extrusive equivalent of monzonite.
Limestone
Limestone is a sedimentary rock consisting chiefly of calcium carbonate, formed from shells and mud on ocean and lake bottoms, and widely used to make Portland cement and lime.
List of rock formations
The list of rock formations gathers notable scenic rocks, from Balanced Rock and Delicate Arch in Utah to the Burren in Ireland, and explains how erosion shapes them.
List of rock types
The list of rock types, also called types of rocks, catalogs the named rocks in the three classes by origin: igneous, sedimentary, and metamorphic, from granite and basalt to schist.
Lithification
Lithification is the conversion of loose sediment into solid sedimentary rock, typically through compaction and cementation by minerals from pore waters, forming rocks such as sandstone and limestone.
Lithology
Lithology is the description of rocks by observable physical characteristics such as color, mineral composition, grain size, texture, and degree of cementation; it defines lithostratigraphic units.
Maevarano Formation
Maevarano Formation: Late Cretaceous (Maastrichtian, 72.1-66 Ma) fossil-rich rock unit in Madagascar's Mahajanga Basin, near Berivotra; source of Majungasaurus, Rapetosaurus, Rahonavis, Beelzebufo; distinct from the Maevarano Suite granites.
Mafic
Mafic, also known as basic rock, describes dark-colored igneous rocks and minerals rich in magnesium and iron, such as basalt and gabbro, contrasting with felsic rocks.
Magnesian Limestone
Magnesian Limestone is a Permian succession of dolomites deposited about 255 million years ago on the margins of the Zechstein Sea, outcropping from Nottinghamshire to County Durham.
Makrana marble
Makrana marble is a white calcite marble quarried at Makrana in Rajasthan, India, the stone of the Taj Mahal and Asia's first Global Heritage Stone Resource in 2023.
Marble
Marble is a metamorphic rock formed when limestone or dolostone recrystallizes under heat and pressure, prized for sculpture and architecture since antiquity for its polish and workability.
Marl
Marl is a calcareous clay, a mixture of calcium carbonate with clay or mud, much of it deposited in lakes and used as a natural liming material.
Metamorphic facies
A metamorphic facies is a set of mineral assemblages that characterizes a range of pressure and temperature conditions during metamorphism, a concept introduced by Finnish geologist Pentti Eskola in 1915.
Metamorphic grade
Metamorphic grade is the relative intensity of metamorphism recorded in a rock, used as a qualitative proxy for metamorphic temperature; index minerals such as garnet and staurolite mark increasing grades.
Metamorphic rock
Metamorphic rock, or metamorphosed rock, forms when heat, pressure, or hot fluids transform pre-existing rock in the solid state deep in the crust, producing rocks such as marble, slate, schist, and gneiss.
Metamorphism
Metamorphism is the geological process that changes pre-existing rocks in mineralogy and texture through heat, pressure, and fluids, without melting them, deep in the Earth's crust.
Metasomatism
Metasomatism is the transformation of a rock's chemical composition through reactions with infiltrating fluids, distinguishing it from metamorphism and forming skarns and many ore deposits.
Micrite
Micrite is a limestone composed of microcrystalline calcite, or carbonate mud with grains typically 1 to 4 μm, named by Robert L. Folk in 1959 for his carbonate rock classification.
Microbialite
A microbialite is an organosedimentary deposit that accretes through interaction between benthic microbial communities and sediments, a term introduced by Burne and Moore in 1987 that includes stromatolites and thrombolites.
middle Kaub Formation
Middle Kaub Formation: clay-rich middle part of the Kaub Formation (Lower Emsian, Lower Devonian) in the Hunsrück, Germany; five members, laminated slates with Chondrites, source of the Bundenbach Hunsrück Slate fossils.
Migmatite
Migmatite is a composite metamorphic rock with two or more distinct parts, at least one formed by partial melting, named by Jakob Johannes Sederholm in 1907 from the Greek for mixture.
Mirambel Formation
Mirambel Formation (Formación Mirambel), a Barremian Lower Cretaceous unit in the Maestrazgo Basin, Iberian Chain, NE Spain; about 200 m of alternating alluvial and lacustrine facies, rich in dinosaur bones, tracks, and eggshells, including Portellsaurus sosbaynati.
Monzogranite
Monzogranite is a variety of granite, a coarse-grained plutonic igneous rock containing 20 to 60 percent quartz and roughly equal amounts of alkali feldspar and plagioclase, defined in the QAPF classification.
Monzonite
Monzonite is a coarse-grained plutonic igneous rock in which alkali feldspar and plagioclase occur in roughly equal amounts, with little quartz; it sits between syenite and diorite.
Mudstone
Mudstone is a fine-grained sedimentary rock of hardened mud, essentially shale without its fine lamination or ability to split into thin flakes, making up much of the sedimentary record.
Mudstone (carbonate)
Mudstone, in carbonate geology, is a mud-supported limestone or carbonate rock with less than 10 percent grains, the finest-grained class of Robert J. Dunham's 1962 depositional-texture classification, formed in low-energy settings.
Mylonite
Mylonite is a fine-grained, cohesive, foliated fault rock formed by ductile deformation in shear zones, coined by Charles Lapworth in 1885 along Scotland's Moine Thrust.