Mineral Resources On-Line Spatial Data
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The MRDS is a large and complex relational database developed over several decades by hundreds of researchers and reporters. This product is a digest in which the fields chosen are those most likely to contain valid information.
Field Missing values Label Number Percent ----------------------------------- DEP_ID 0 0.0 MRDS_ID 149235 49.0 MAS_ID 110652 36.4 SITE_NAME 0 0.0 LATITUDE 4033 1.3 LONGITUDE 4033 1.3 REGION 58555 19.2 COUNTRY 58555 19.2 STATE 58762 19.3 COUNTY 65215 21.4 DISTRICT 254769 83.7 ADMIN 299777 98.5 LAND_STAT 114367 37.6 COM_TYPE 34 0.0 COM_MAJOR 22335 7.3 COM_MINOR 285184 93.7 COM_TRACE 239278 78.6 OPER_TYPE 0 0.0 DEP_TYPE 269516 88.6 PROD_SIZE 194976 64.1 DEV_STAT 0 0.0 ORE 236479 77.7 GANGUE 272740 89.6 OTHER_MATL 294207 96.7 OREBODY_FM 264927 87.1 WORK_TYPE 238249 78.3 MODEL 292387 96.1 ALTERATION 289757 95.2 CONC_PROC 293637 96.5 PREV_NAME 241287 79.3 ORE_CTRL 279810 91.9 REPORTER 36 0.0 HROCK_UNIT 268180 88.1 HROCK_CODE 236050 77.6 AROCK_UNIT 291593 95.8 AROCK_CODE 278263 91.4 STRUCTURE 280348 92.1 TECTONIC 285058 93.7 REF 25211 8.3
Review of many database fields resulted in significant simplification, harmonization among records within these databases and between the databases, and elimination of duplicate records.
The resulting relational database is currently maintained by William Ferguson under the supervision of Paul Schruben.
Select fields and tables from the Oracle RDBMS are extracted using the script pull.php to produce local copies of the tables containing only those fields needed to produce the current digest.
The script combine.php draws data from these local tables to create a single monolithic table with one row per mineral resource record.
At this writing a number of corrections are made to the data given for the form of orebodies. These changes include the elimination of the useless value "SEE DEPOSIT DESCRIPTION COMMENTS", the elimination of empty parentheses from most records, replacement of the abbreviation 'IRREG' with the more common complete value 'IRREGULAR', and especially a complex analysis of most values originating in the MAS/MILS database. These changes are described by the script orebody-fix.php.
Additional modifications are made to the geographic locations of about 4300 records whose coordinates are given in the source database as the South Pole. These coordinates are replaced with NULL values in the current database. The data selection software in the current distribution web site allows some of these records to be retrieved because some of the records contained additional information linking them to specific geographic areas. These changes are carried out by the script place-fix.php.
Information about host rocks and associated rocks was subject to additional correction using the SQL statements in fix-rock.php.
This table is used to create the GIS shapefiles and other formats available for download.
A unique 12-digit system generated sequence number which references records of information pertaining to a mineral property. Textual values of no more than 12 characters.
Identification number used to refer to this entry in the Mineral Resources Data System, if the record appeared in that database. Textual values of no more than 7 characters.
Identification number for this site as it appeared in the Mineral Availability System/Mineral Industry Locator System database,. Textual values of no more than 10 characters.
Current (preferred) form of the name of the site, deposit, or operation to which the record refers. Textual values of no more than 70 characters.
Geographic latitude of the site (no specific datum applies; use NAD27 if needed). Real numbers stored in double precision.
Geographic longitude of the site (no specific datum applies; use NAD27 if needed). Real numbers stored in double precision.
Code indicating the geographic region. Textual values of no more than 2 characters.
Name of the country in which the site is located. Textual values of no more than 20 characters.
Name of the state or province in which the site is located. Textual values of no more than 32 characters.
Name of the county in which the site is located. Textual values of no more than 96 characters.
The most recent name of the mining district, subdistrict, or area. Textual values of no more than 96 characters.
Administrative unit area name. The area type is given in the LAND_STAT field. Textual values of no more than 160 characters.
Type of geographic area named in ADMIN. Textual values of no more than 35 characters.
Type of commodities present: metallic (M), non-metallic (N), or both (B). Textual values of no more than 1 characters.
Major commodities present, a comma-separated list. Commodity qualifiers follow each commodity, delimited by a hyphen. Textual values of no more than 128 characters.
Minor commodities present, a comma-separated list. Commodity qualifiers follow each commodity, delimited by a hyphen. Textual values of no more than 128 characters.
Trace commodities present, a comma-separated list. Commodity qualifiers follow each commodity, delimited by a hyphen. Textual values of no more than 128 characters.
Type of operation existing or proposed at the site. Textual values of no more than 30 characters.
General type of deposit or resource present at the site. Textual values of no more than 40 characters.
A broad characterization of the magnitude of production at the site. Textual values of no more than 12 characters.
Status of development of the resource or operation. Textual values of no more than 25 characters.
Name of the ore mineral or material found in this deposit. Textual values of no more than 255 characters.
Name of the gangue mineral or material found in this deposit. Textual values of no more than 255 characters.
Name of other minerals or materials found in this deposit. Textual values of no more than 255 characters.
Form and shape of the ore body. Textual values of no more than 255 characters.
General type of workings at the site. Textual values of no more than 64 characters.
Mineral deposit models that characterize the site. Multiple models are delimited by braces, with a model number for each. Textual values of no more than 80 characters.
Geochemical alteration, if any, believed to have been important in forming or modifying the ore materials of a deposit. Textual values of no more than 255 characters.
Geological processes that are believed to have occurred to concentrate ore materials in the deposit. Textual values of no more than 255 characters.
Names by which the site or operation has bee known in the past. Textual values of no more than 255 characters.
Geologic features, typically structural, that exert control over the form, extent, or character of the deposit. Textual values of no more than 255 characters.
Names of the persons primarily responsible for entering information about the site. Textual values of no more than 224 characters.
Lithologic and stratigraphic information regarding the host rocks for the ore deposit. Textual values of no more than 255 characters.
Integer number(s) indicating the type of host rocks. Textual values of no more than 40 characters.
Dominantly unsorted and unstratified drift, generally unconsolidated, deposited directly by and underneath a glacier without subsequent reworking by meltwater
A general term for clay, silt, sand, gravel or similar unconsolidated detrital material, deposited during comparatively recent geologic time by a stream or other body of running water, as a sorted or semi-sorted sediment.
A loose aggregate of unlithified mineral or rock particles of sand size forming a beach (the relatively thick and temporary accumulation of loose water-borne material that is in active transit along, or deposited on, the shore zone between the limits of low water and high water)
A type of blown sand that has been piled up by the wind into a sand dune, usually consisting of rounded mineral grains, commonly quartz, having diameters ranging from 0.1 to 1 mm
A widespread, homogeneous, commonly nonstratified, porous, friable, slightly coherent, usually highly calcareous, fine-grained blanket deposit, consisting predominantly of silt with subordinate grain sizes ranging from clay to fine sand.
A fine pyroclastic material (under 2.0 mm in diameter). The term usually refers to the unconsolidated material
A general term applied to any loose, heterogeneous, and incoherent mass of soil material and/or rock fragments deposited by rainwash, sheetwash, or slow, continuous downslope creep, usually collecting at the base of gentle slopes or hillsides.
Dominantly unsorted and unstratified drift, generally unconsolidated, deposited directly by and underneath a glacier without subsequent reworking by meltwater
Stratified glacial drift deposited by, or reworked by running water, or deposited in standing water
An unconsolidated deposit of semicarbonized plant remains in a water saturated environment, such as a bog or fen, and of persistently high moisture content (at least 75 percent).
A hard calcareous substance consisting of the continuous skeleton secreted by coral polyps for their support and habitation and found in single specimens growing plant-like on the sea bottom or in extensive, solidified accumulations (coral reefs).
A loose, earthy, extremely fine-grained, natural sediment composed primarily of clay-size or colloidal particles and characterized by high plasticity and by a considerable content of clay minerals.
A loose aggregate of unlithified mineral or rock particles of silt size (1/256 to 1/16 mm); an unconsolidated deposit consisting essentially of fine-grained clastic particles.
A loose aggregate of unlithified mineral or rock particles of sand size (1/16 to 2 mm); an unconsolidated deposit consisting essentially of medium-grained clastic particles.
A loose accumulation of rock fragments composed predominantly of more or less rounded pebbles and small stones.
A loose aggregate of unlithified mineral or rock particles of sand size (1/16 to 2 mm); an unconsolidated deposit consisting essentially of medium-grained clastic particles, plus a loose accumulation of rock fragments composed predominantly of more or less rounded pebbles and small stones.
Saline waters containing high amounts of Na, Ca, K, Cl, and other soluble elements.
The surface of the rock or sediments at the bottom of the sea.
A rock resulting from the consolidation of loose sediment that has accumulated in layers
A composed principally of broken fragments that are derived from preexisting rocks or minerals and that have been transported some distance from their place of origin.
A general term that includes claystone, siltstone, shale, and argillite, and that should be used only when the amounts of clay-sized and silt-sized particles are not known or specified, or cannot be precisely identified.
An indurated rock having more than 67 percent clay-sized minerals.
A soft, plastic, porous, light-colored rock composed essentially of clay minerals of the montmorillonite (smectite) group plus colloidal silica, and produced by devitrification and accompanying chemical alteration of a glassy igneous material, usually a tuff or volcanic ash
A laminated, indurated rock having more than 67 percent clay-sized minerals.
A dark, thinly laminated carbonaceous shale, exceptionally rich in organic matter (5 percent or more carbon content) and sulfide (esp. iron sulfide, usually pyrite), and often containing unusual concentrations of certain trace elements (U, V, Cu, Ni).
A kerogen-bearing, finely laminated brown or black sedimentary rock that will yield liquid or gaseous hydrocarbon on distillation.
A compact rock derived either from mudstone or shale, that has undergone a somewhat higher degree of induration than mudstone or shale but is less clearly laminated than shale and without its fissility, and that lacks the cleavage distinctive of slate.
An indurated silt having the texture and composition of shale but lacking its fine lamination or fissility; a massive mudstone in which silt-sized particles predominate over clay-sized particles.
A medium-grained clastic sedimentary rock composed of abundant sand-sized fragments, which may have a finer-grained matrix (silt or clay), and which is more or less indurated by a cementing material
A clastic sedimentary rock that is made up almost exclusively of quartz sand (with or without chert), that is relatively free of or lacks a fine-grained matrix; a quartzite of sedimentary origin, or a "pure quartz sandstone".
A clastic sedimentary rock that is made up predominantly of recycled carbonate particles of sand size; a consolidated calcareous sand
A feldspar-rich sandstone, commonly coarse-grained and pink or reddish, that is typically composed of angular to subangular grains that may be either poorly or moderately well sorted. Quartz is usually the dominant mineral, with feldspars constituting at least 25 percent.
A "dirty" sandstone that consists of a mixed variety of unsorted or poorly sorted mineral and rock fragments and of an abundant matrix of clay and fine silt; specif. an impure sandstone containing more than 10 percent argillaceous matrix.
a dark gray, firmly indurated, coarse-grained sandstone that consists of poorly sorted angular to subangular grains of quartz and feldspar, with a variety of dark rock and mineral fragments embedded in a compact clayey matrix having the general composition of slate and containing an abundance of very fine-grained illite, sericite, and chloritic minerals.
A coarse-grained clastic sedimentary rock, composed of rounded to subangular fragments larger than 2 mm in diameter typically containing fine-grained particles in the interstices, and commonly cemented by calcium carbonate, iron oxide, silica, or hardened clay
A breccia (coarse-grained clastic rock composed of angular broken rock fragments held together by a mineral cement or a fine-grained matrix) formed by sedimentary processes
A sedimentary deposit consisting of a chaotic mass of intimately mixed heterogeneous materials (such as blocks and muds) that accumulated as a semi-fluid body by submarine gravity sliding or slumping of unconsolidated sediments.
Sediments laid on the floor of a lake, usually coarse grainde near shore and rapidly changing to fine-grained clay and limesone in deeper water.
A sedimentary rock composed of more than 50 percent by weight carbonate minerals
A sedimentary rock consisting chiefly (more than 50 percent by weight or by areal percentages under the microscope) of calcium carbonate, primarily in the form of the mineral calcite.
A carbonate sedimentary rock of which more than 50 percent by weight or by areal percentages under the microscope consists of the mineral dolomite
An undivided mixture of clastic and carbonate sedimentary rocks.
An undivided mixture of clastic and carbonate sedimentary rocks.
A sedimentary rock with a high enough content of phosphate minerals to be of economic interest.
A sedimentary rock composed primarily of material formed directly by precipitation from solution or colloidal suspension or by the deposition of insoluble precipitates
A nonclastic sedimentary rock composed primarily of minerals produced from a saline solution as a result of extensive or total evaporation of the solvent.
An evapotite primarily composed of sodium chloride.
A hard, extremely dense or compact, dull to semivitreous, microcrystalline or cryptocrystalline sedimentary rock, consisting dominantly of interlocking crystals of quartz less than 30 cm in diameter.
A chemical sedimentary rock, typically thin-bedded and/or finely laminated, containing at least 15 percent iron of sedimentary origin, and commonly but not necessarily containing layers of chert
A chemical sedimentary rock, usually containing oxide, carbonate, or sulfide as anions, and iron, magnesium, base metals, and gold as cations, formed by the issuance of volcanically derived fluids onto the sea floor or into the sea
A readily combustible rock containing more than 50 percent by weight and more than 70 percent by volume carbonaceous material, formed by compaction and induration of variously altered plant remains
A light-colored,soft, friable, siliceous sedimentary rockconsisting chiefly of opaline frustules of the diatom.
A generally finely crystalline or glassy igneous rock resulting from volcanic action at or near the Earth's surface, either ejected explosively or extruded as a lava. The term includes near-surface intrusions that form a part of the volcanic structure.
Extrusive rock having a texture which is similar to that of glass or quartz and developed as a result of rapid cooling of the lava without distinct crystallization.
A black or dark-colored volcanic glass, usually of rhyolite composition, characterized by conchoidal fracture
Any porphyritic igneous rock having a glassy groundmass.
A light-colored vesicular glassy rock commonly having the composition of rhyolite.
Clastic rock material formed by volcanic explosion or aerial expulsion from a volcanic vent.
Consolidated or cemented volcanic ash.
A glass-rich pyroclastic rock that has been indurated by the welding together of its glass shards under the combined action of the heat retained by particles, the weight of the overlying material, and hot gasses.
A tuff deposited by an ash flow or gaseous cloud; a type of ignimbrite. It is a consolidated, but not necessarily welded deposit.
The deposit of a pyroclastic flow.
A pyroclastic rock that consists of angular volcanic fragments that are larger than 64 mm in diameter and that may or may not have a matrix
A light-colored, fine-grained or aphanitic extrusive or hypabyssal rock, with or without phenocrysts and composed chiefly of quartz and feldspar.
A volcanic rock defined in the QAPF diagram as having Q/(Q+A+P) between 20 and 60 and P/(P+A) less than 10.
A volcanic rock defined in the QAPF diagram as having Q/(Q+A+P) between 20 and 60 and P/(P+A) between 10 and 35.
A volcanic rock defined in the QAPF diagram as having Q/(Q+A+P) between 20 and 60 and P/(P+A) between 35 and 65.
A volcanic rock defined in the QAPF diagram as having Q/(Q+A+P) between 20 and 60 and P/(P+A) greater than 65.
A volcanic rock defined in the QAPF diagram as having Q/(Q+A+P) less than 20 or F/(F+A+P) less than 10, and P/(P+A) less than 10.
A volcanic rock defined in the QAPF diagram as having Q/(Q+A+P) less than 20 or F/(F+A+P) less than 10, and P/(P+A) between 10 and 35.
A volcanic rock defined in the QAPF diagram as having Q/(Q+A+P) between 5 and 20 and P/(P+A) between 35 and 65.
A volcanic rock defined in the QAPF diagram as having Q/(Q+A+P) less than 5 or F/(F+A+P) less than 10, and P/(P+A) between 35 and 65.
A solidified body of volcanic rock having approximately equal light- and dark-colored minerals in its mode
A volcanic rock defined modally by Q/(Q+A+P) less than 20 or F/(F+A+P) less than 10, P/(A+P) between 65 and 90, and M less than 35.
A volcanic rock defined modally by Q/(Q+A+P) less than 20 or F/(F+A+P) less than 10, P/(A+P) greater than 90, and M less than 35
A solidified body of volcanic rock having abundant dark-colored minerals in its mode
A volcanic rock defined modally by Q/(Q+A+P) less than 20 or F/(F+A+P) less than 10, P/(A+P) between 65 and 90, and M greater than 35.
A volcanic rock defined modally by Q/(Q+A+P) less than 20 or F/(F+A+P) less than 10, P/(A+P) greater than 90, and M greater than 35.
A silica-oversaturated basalt, characterized by the presence of low-calcium pyroxenes in addition to clinopyroxene and calcic plagioclase. Olivine may be present in the mode, but neither olivine nor nepheline appear in the norm.
A basalt in which the normative and modal feldspar is andesine, and with soda:potash ratio greater than 2:1. It generally, but not always, lacks normative quartz, and commonly contains normative and modal olivine.
A basalt with nepheline and/or acmite in the CIPW norm.
A volcanic rock that contains more sodium and/or potassium than is required to form feldspar with the available silica.
A volcanic rock defined in the QAPF diagram as having F/(F+A+P) between 10 an 60, and P/(P+A) less than 10.
A volcanic rock defined in the QAPF diagram as having F/(F+A+P) between 10 an 60, and P/(P+A) greater than 90.
A volcanic rock with color index (M) greater than or equal to 90
A rock of apparent volcanic origin composed of at least 50 percent carbonate minerals
A rock formed at considerable depth by crystallization of magma and/or by chemical alteration. It is characteristically medium- to coarse-grained, of granitoid texture.
A light-colored igneous rock characterized by a fine-grained allotriomorphic-granular (i.e. aplitic) texture.
An igneous rock of any composition that contains conspicuous phenocrysts in a fine-grained groundmass
A group of porphyritic igneous rocks in which mafic minerals form the phenocrysts; feldspars, if present, are restricted to the groundmass
An exceptionally coarse-grained igneous rock, with interlocking crystals, usually found as irregular dikes, lenses, or veins, esp. at the margins of batholiths
A general term for all phaneritic igneous rocks dominated by quartz and feldspars
A plutonic rock defined in the QAPF diagram as having Q between 20 and 60 and P/(A+P) less than 10
A plutonic rock defined in the QAPF diagram as having Q between 20 and 60 and P/(A+P) between 10 and 65
A granite with aluminum oxide greater than sodium oxide + potassium oxide + calcium oxide; typical accessories include: muscovite, biotite, corundum, topaz, garnet
A granite with aluminum oxide greater than sodium oxide + potassium oxide, but with aluminum oxide less than sodium oxide + potassium oxide + calcium oxide; typical accessories include: hornblende, epidote, melilite, or biotite + pyroxene
A granite with aluminum oxide approximately equal to sodium oxide + potassium oxide; typical accessories include: olivine, orthopyroxene, clinopyroxene
A granite with aluminum oxide less than sodium oxide + potassium oxide; typical accessories include: soda pyroxene and soda amphibole[
A plutonic rock defined in the QAPF diagram as having Q between 20 and 60 and P/(A+P) between 65 and 90
A plutonic rock defined in the QAPF diagram as having Q between 20 and 60 and P/(A+P) greater than 90
A tonalite with color index (M) less than 15; composed essentially of sodic plagioclase, quartz, sparse biotite, and little or no alkali feldspar
A plutonic rock defined in the QAPF diagram as having Q/(Q+A+P) less than 20 or F/(F+A+P) less than 10, and P/(P+A) less than 10
A plutonic rock defined in the QAPF diagram as having Q between 5 and 20 and P/(A+P) between 10 and 35
A plutonic rock defined in the QAPF diagram as having Q between 5 and 20 and P/(A+P) between 35 and 65
A plutonic rock defined in the QAPF diagram as having Q between 5 and 20 and P/(A+P) between 65 and 90, and plagioclase more sodic than An50
A plutonic rock defined in the QAPF diagram as having Q less than 5 or F/(F+A+P) less than 10, and P/(A+P) between 35 and 65
An igneous rock composed chiefly of one or more dark ferromagnesian minerals. An exception is made for anorthosite, which occurs in association with mafic rocks.
A plutonic rock defined in the QAPF diagram as having Q between 5 and 20 and P/(A+P) between 65 and 90, and plagioclase more sodic than An50
A plutonic rock defined in the QAPF diagram as having Q between 5 and 20 and P/(A+P) between 65 and 90, and plagioclase more calcic than An50
A plutonic rock defined in the QAPF diagram as having Q less than 5 or F/(F+A+P) less than 10, and P/(A+P) between 65 and 90, and plagioclase more sodic than An50
A plutonic rock defined in the QAPF diagram as having Q less than 5 or F/(F+A+P) less than 10, and P/(A+P) between 65 and 90, and plagioclase more calcic than An50
A plutonic rock defined in the QAPF diagram as having Q between 5 and 20, P/(A+P) greater than 90, and plagioclase more sodic than An50
A plutonic rock defined in the QAPF diagram as having Q between 5 and 20, P/(A+P) greater than 90, and plagioclase more calcic than An50
A plutonic rock defined in the QAPF diagram as having Q between 0 and 5 or F/(F+A+P) less than 10, P/(A+P) greater than 90 and plagioclase more sodic than An50
A plutonic rock whose main components are labradorite and pyroxene and which is characterized by ophitic texture
A plutonic rock defined in the QAPF diagram as having Q between 0 and 5 or F/(F+A+P) less than 10, P/(A+P) greater than 90 and plagioclase more calcic than An50
A plutonic rock satisfying the definition of gabbro, in which pl/(pl+px+ol) is between 10 and 90 and opx/(opx+cpx) is greater than 95.
A plutonic rock satisfying the definition of gabbro, in which pl/(pl+px+ol) is between 10 and 90 and px/(pl+px+ol) is less than 5.
A plutonic rock defined in the QAPF diagram as having Q between 0 and 5, P/(A+P) greater than 90, and M less than 10. A group of monomineralogic plutonic igneous rocks composed almost entirely of plagioclase feldspar.
A plutonic rock that contains more sodium and/or potassium than is required to form feldspar with the available silica
A plutonic rock defined in the QAPF diagram as having F/(F+A+P) between 10 and 60, and P/(P+A) less than 50; composed essentially of alkali feldspar and nepheline
A general name for plutonic rock with color index (M) greater than or equal to 90
A plutonic rock with M equal to or greater than 90 and ol/(ol+opx+cpx) greater than 40
A plutonic rock with M equal to or greater than 90 and ol/(ol+opx+cpx) greater than 90
A plutonic rock with M equal or greater than 90, ol/(ol+opx+cpx) greater than 40, and cpx/(ol+opx+cpx) less than 5.
A plutonic rock with M equal or greater than 90, ol/(ol+opx+cpx) greater than 40, and opx/(ol+opx+cpx) less than 5.
A plutonic rock with M equal or greater than 90, ol/(ol+opx+cpx) greater than 40, and opx roughly equal to cpx.
A porphyritic alkalic peridotite containing abundant phenocrysts of olivine and phlogopite, and possibly geikielite and chromian pyrope, in a fine-grained groundmass of calcite and second-generation olivine and phlogopite.
A plutonic rock with M equal to or greater than 90 and pyroxene/(ol+pyroxene) greater than 90.
A plutonic rock with M equal to or greater than 90 and cpx/(ol+opx+cpx) greater than 90.
A plutonic rock with M equal to or greater than 90 and opx/(ol+opx+cpx) greater than 90.
A plutonic rock with M equal to or greater than 90 and hbl/(hbl+px+ol) greater than 90.
A plutonic rock composed of at least 50% carbonate minerals.
A rock derived from pre-existing rocks by mineralogical, chemical, and/or structural changes, essentially in the solid state, in response to marked changes in temperature, pressure, shearing stress, and chemical environment, generally at depth in the earth's crust.
A fine-grained rock composed of a mosaic of equidimensional grains without preferred orientation and typically formed by contact metamorphism.
A sedimentary rock that shows evidence of having been subjected to metamorphism
An argillite that has been metamorphosed.
A compact, fine-grained metamorphic rock that possesses slaty cleavage and hence can be split into slabs and thin plates
A granoblastic metamorphic rock consisting mainly of quartz and formed by recrystallization of sandstone or chert by either regional or thermal metamorphism.
A metamorphic rock consisting predominantly of fine- to coarse-grained recrystallized calcite and/or dolomite, usually with a granoblastic, saccharoidal texture
A volcanic rock that shows evidence of having been subjected to metamorphism.
A metavolcanic rock having abundant light-colored minerals, typically quartz and feldspar
A low-grade, felsic metavolcanic rock with preserved evidence of its original rhyolitic character
All salic extrusive and hypabyssal rocks characterized by the presence of albite or albite-oligoclase and chlorite, epidote, and calcite, generally of secondary order.
A metavolcanic rock having abundant dark-colored minerals, typically feldspar, amphibole, and/or pyroxene
A low-grade, mafic metavolcanic rock with preserved evidence of its original basaltic character
An altered basalt, characteristically amygdaloidal or vesicular, in which the feldspar has been albitized and is typically accompanied by chlorite, calcite, epidote, chalcedony, prehnite, or other low-temperature hydrous crystallization products characteristic of a greenstone.
A field term applied to any compact, dark-green, altered or metamorphosed basic igneous rock (e.g. spilite, basalt, gabbro, diabase) that owes its color to the presence of chlorite, actinolite, or epidote.
A metamorphosed rock, intermediate in grade between slate and mica schist. Minute crystals of graphite, sericite, or chlorite impart a silky sheen to the surfaces of cleavage (or schistosity).
A strongly foliated crystalline rock, formed by dynamic metamorphism, that can be readily split into thin flakes or slabs due to the well developed parallelism of more than 50 percent of the minerals present, particularly those of the lamellar or elongate prismatic habit, e.g. mica and hornblende.
A schistose metamorphic rock whose green color is due to the presence of chlorite, epidote, or actinolite; a common product of low-grade regional metamorphism of pelitic or basic igneous rocks
A schistose metamorphic rock with a blue color owing to the presence of sodic amphibole, glaucophane, or crossite, and commonly mottled bluish-gray lawsonite; characteristic of metamorphism in areas of unusually low thermal gradient, such as subduction zones
A schist whose essential constituents are mica and quartz, and whose schistosity is mainly due to the parallel arrangement of mica flakes.
A schistose metamorphic rock derived by metamorphism of an argillaceous or a fine-grained alluminous sediment.
A schist whose essential constituents are quartz and feldspar and having lesser amounts of mica and/or hornblende
A metamorphosed calcareous rock, commonly derived from argillaceous limestone or calcareous mudstone, containing calcium-bearing silicates such as diopside and wollastonite, with a schistose structure produced by parallelism of platy minerals
A schist whose essential constituent is amphibole with lesseramounts of feldspar, quartz, and/or mica
