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Geologic units containing greenstone

Earth material > Metamorphic rock > Metavolcanic rock > Mafic metavolcanic rock
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.
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Alabama - Arizona - California - Connecticut - Idaho - Massachusetts - Maryland - Maine - North Carolina - New Hampshire - New Jersey - Nevada - New York - Oregon - Rhode Island - South Carolina - South Dakota - Virginia - Vermont - Washington - West Virginia
Alabama
Hillabee Greenstone (Paleozoic)
Hillabee Greenstone - pale-green to light-olive-brown massive, fine-grained greenstone interbedded locally with well-foliated mafic phyllite.
Arizona
Early Proterozoic metavolcanic rocks (Early Proterozoic)
Weakly to strongly metamorphosed volcanic rocks. Protoliths include basalt, andesite, dacite, and rhyolite deposited as lava or tuff, related sedimentary rock, and shallow intrusive rock. These rocks, widely exposed in several belts in central Arizona, include metavolcanic rocks in the Yavapai and Tonto Basin supergroups. (1650 to 1800 Ma)
California
Carboniferous marine rocks, unit 4 (Eastern Klamath Mountains) (Mississippian to Early Permian)
Shale, sandstone, conglomerate, limestone, dolomite, chert, hornfels, marble, quartzite; in part pyroclastic rocks
Franciscan Complex, unit 1 (Coast Ranges) (Jurassic to Cretaceous)
Franciscan complex: Cretaceous and Jurassic sandstone with smaller amounts of shale, chert, limestone, and conglomerate. Includes Franciscan melange, except where separated--see KJfm.
Mesozoic volcanic rocks, unit 1 (Coast Ranges) (Jurassic to Cretaceous)
Undivided Mesozoic volcanic and metavolcanic rocks. Andesite and rhyolite flow rocks, greenstone, volcanic breccia and other pyroclastic rocks; in part strongly metamorphosed. Includes volcanic rocks of Franciscan Complex: basaltic pillow lava, diabase, greenstone, and minor pyroclastic rocks
Paleozoic marine rocks, undivided, unit 6 (Northwestern Sierra Nevada) (Permian(?) to Jurassic(?))
Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite
Paleozoic metavolcanic rocks, unit 6 (El Paso Mountains) (Devonian(?) and Permian)
Undivided Paleozoic metavolcanic rocks. Mostly flows, breccia and tuff, including greenstone, diabase, and pillow lavas; minor interbedded sedimentary rocks
Undivided pre-Cenozoic metavolcanic rocks, unit 2 (undivided) (Paleozoic(?) to Mesozoic(?))
Undivided pre-Cenozoic metavolcanic rocks. Includes latite, dacite, tuff, and greenstone; commonly schistose.
Connecticut
Allingtown Metavolcanics (Middle? Ordovician)
Allingtown Metavolcanics - Green, fine-grained, massive greenstone, composed of epidote, actinolite, albite, and chlorite, commonly with abundant megacrysts of saussurite, interlayered with minor green phyllite, generally containing quartz and sericite. Dark amphibole in western outcrops.
Allingtown Metavolcanics plus Maltby Lakes Metavolcanics (Middle? Ordovician)
Allingtown Metavolcanics plus Maltby Lakes Metavolcanics - Allingtown Metavolcanics - Green, fine-grained, massive greenstone, composed of epidote, actinolite, albite, and chlorite, commonly with abundant megacrysts of saussurite, interlayered with minor green phyllite, generally containing quartz and sericite. Dark amphibole in western outcrops. Maltby Lakes Metavolcanics - Green to gray-green, fine-grained, massive to well-foliated and layered greenstone, greenschist, and schist; also dark amphibolite to west and southwest.
Lower part [of Maltby Lakes Metavolcanics] (Middle? Ordovician)
Lower part [of Maltby Lakes Metavolcanics] - Gray-green to green, fine-grained, generally well foliated greenschist, greenstone, and schist or phyllite, composed of albite and chlorite, plus quartz and sericite or epidote and actinolite. Mixed metavolcanics and metasedimentary rocks.
Maltby Lakes Metavolcanics (Middle? Ordovician)
Maltby Lakes Metavolcanics - Green to gray-green, fine-grained, massive to well-foliated and layered greenstone, greenschist, and schist; also dark amphibolite to west and southwest.
Oronoque Schist (Lower? Ordovician)
Oronoque Schist - Gray to silver, medium- to fine-grained, well-layered to laminated schist and granofels, composed of quartz, oligoclase, or albite, muscovite or sericite, biotite, or chlorite, and in western belt local garnet, staurolite, and kyanite. Small lenses of amphibolite or greenstone.
Upper part [of Maltby Lakes Metavolcanics] (Middle? Ordovician)
Upper part [of Maltby Lakes Metavolcanics] - Green to gray-green, fine-grained, layered and foliated to massive greenstone and greenschist, composed of epidote, albite, actinolite, and chlorite, and locally minor quartz, sericite, garnet, pyrite, or calcite. Mainly metavolcanic.
Idaho
Metasedimentary and meta-igneous rocks; Triassic to Mississippian greenschist-facies dismembered ophiolite, western Idaho, Blue Mountains island-arc complex (Triassic to Mississippian)
Jurassic marine wacke, volcanic, or carbonate metasediments of western Idaho.
Metavolcanic and metasedimentary rocks; Jurassic greenschist-facies metamorphic rocks; western Idaho, Blue Mountains island-arc complex (Jurassic)
Jurassic mixed marine detrital and volcanic rocks of western Idaho.
Massachusetts
Blackstone Group (Proterozoic Z)
Blackstone Group - Greenstone and amphibolite - Includes Hunting Hill Greenstone.
Hawley Formation (Middle Ordovician)
Hawley Formation - Interbedded amphibolite, greenstone, feldspathic schist and granofels. Coarse plagioclase in some amphibolite near top; local coarse hornblende blades or sprays. Sparse coticule (Emerson, 1917, p. 43). As used here the Hawley includes amphibolite, sulfidic rusty schists, abundant coticules, silvery schists, quartzites and quartz conglomerates, and quartz, feldspar, biotite granulites. The quartzites and quartz conglomerates occur at two positions in rocks here assigned to the Hawley. Those occurring near the top have been mapped previously as Russell Mountain Formation or as Shaw Mountain Formation. The Hawley overlies the Ordovician Barnard Gneiss and underlies Silurian and Devonian "calciferous schists" that include the westernmost Goshen Formation in MA and Northfield Formation in southern VT, the central Waits River Formation and the eastern Gile Mountain Formation. Authors believe that the Goshen, Northfield, and Waits River are facies equivalents, while the Gile Mountain is slightly younger. Map symbol indicates that Hawley is Ordovician and Silurian. 40Ar/3Ar hornblende release spectrum date of 433+/-3 Ma obtained by Spear and Harrison (1989) (Trzcienski and others, 1992).
Moretown Formation (Middle Ordovician or older)
Moretown Formation - Green to dark-green greenstone or amphibolite.
Maryland
Ijamsville Formation (Late Precambrian (?))
Ijamsville Formation - Blue, green, or purple phyllite and phyllitic slate, with interbedded metasiltstone and metagraywacke; flattened pumiceous blebs occur locally.
Volcanic Complex of Cecil County (Late Precambrian (?))
Volcanic Complex of Cecil County - Metamorphosed andesitic and dacitic volcanic rocks (greenstone, greenschist, quartz amphibolite, and schistose felsite); amygdules and volcano-clastic textures locally preserved; thickness unknown.
Maine
Cambrian Jim Pond Formation (Cambrian)
Cambrian Jim Pond Formation
Cambrian Jim Pond Formation mafic volcanic rocks (Cambrian)
Cambrian Jim Pond Formation mafic volcanic rocks
Devonian - Ordovician Spruce Top Greenstone (Devonian - Ordovician)
Devonian - Ordovician Spruce Top Greenstone
Devonian Seboomook Formation Camera Hill Greenstone (Devonian)
Devonian Seboomook Formation Camera Hill Greenstone
Devonian Seboomook Formation unnamed mafic greenstone (Silurian-Devonian)
Devonian Seboomook Formation unnamed mafic greenstone
Ordovician - Precambrian Z Ellsworth formation greenstone member (Ordovician - Precambrian Z)
Ordovician - Precambrian Z Ellsworth formation greenstone member
Precambrian Z North Haven Formation (Precambrian)
Precambrian Z North Haven Formation
Silurian greenstone rocks of the Fivemile Brook sequence (Silurian)
Silurian greenstone rocks of the Fivemile Brook sequence
North Carolina
Blowing Rock Gneiss (Middle Proterozoic)
Blowing Rock Gneiss (1000 my) - unconformity; abundant white potassic feldspar megacrysts in finely banded biotite schist, locally calcareous; interlayered with quartz-feldspar schist, calcareous biotite schist, phyllite, black slate, calcareous quartzite, sulfidic greenstone, and siliceous tuff.
Grandfather Mountain Formation; Metasiltstone (Late Proterozoic)
Greenstone - schistose to massive, amygdaloidal; interlayered with metasedimentary rocks. Includes Montezuma Member (metabasalt) in upper part.
Linville Metadiabase (Late Proterozoic)
Linville Metadiabase - metadiabase, greenstone, and amphibolite dikes and sills; massive to schistose.
Mount Rogers Formation; Metagraywacke (Late Proterozoic)
Metagraywacke - interlayered with metaconglomerate, laminated metasiltstone, and slate; minor calcareous metasandstone, greenstone, and metarhyolite.
New Hampshire
Littleton Formation, Metabasaltic greenstone or amphibolite (Lower Devonian)
Littleton Formation, Metabasaltic greenstone or amphibolite.
New Jersey
Metabasalt (Late Proterozoic)
Metabasalt - Sequence of conformably layered volcanic rocks of fine-grained to aphanitic, greenish-gray, retrogressively metamorphosed greenstone, greenschist, and basalt. Greenschist contains clots and lenses of blue quartz and abundant sulfide. Unit does not crop out and is known only from subsurface borings and artificial exposures. Interpreted to be Late Proterozoic by Volkert and Drake (1993) on the basis of geochemical similarity to Late Proterozoic metadiabase dikes in New Jersey Highlands.
Nevada
Scott Canyon Formation (Early Cambrian to Middle Cambrian)
SCOTT CANYON FORMATION (Lower or Middle Cambrian)-Chert, shale, greenstone, and sparse limestone and quartzite. Southeast Humboldt County and northwest Lander County.
Shale, chert, and minor amounts of quartzite, greenstone, and limestone (Ordovician)
SHALE, CHERT, AND MINOR AMOUNTS OF QUARTZITE, GREENSTONE, AND LIMESTONE-Includes units such as Vinini Formation of north-central Nevada, Palmetto Formation in southern and central parts of Esmeralda County, and Comus Formation in Humboldt County. Locally includes rocks of Silurian and Devonian age.
Siliceous and volcanic rocks (Ordovician to Devonian)
SILICEOUS AND VOLCANIC ROCKS-Chert, shale, quartzite, greenstone, and minor amounts of limestone. Includes units such as Valmy Formation of north-central Nevada and some rocks mapped as Palmetto Formation in northern part of Esmeralda County and adjacent parts of Mineral and Nye Counties. Locally includes rocks of Silurian and Devonian age.
Silty limestone, minor amounts of shale, and some greenstone (Permian to Early Triassic)
SILTY LIMESTONE, MINOR AMOUNTS OF SHALE, AND SOME GREENSTONE-Unnamed sequence in Adobe Range, northern Elko County
New York
Greenstones and tuffs and/or basalt (Cambrian?)
Greenstones and tuffs and/or basalt
Oregon
Condrey Mountain Schist (Triassic? and Paleozoic?) (Paleozoic(?) to Jurassic)
Consists of a variety of schistose rocks characterized by different proportions of muscovite, quartz, graphite, chlorite, actinolite, and epidote, rare thin layers of metachert, and clinozoisite-actinolite-albite-garnet metagabbro. Potassium-argon age on muscovite from unit is about 141 Ma (Lanphere and others, 1968) and on a whole rock sample is about 155 Ma (Suppe and Armstrong, 1972), indicating a Late Jurassic metamorphic age. Protolith is probably Triassic and Paleozoic in age
Otter Point Formation of Dott (1971) and related rocks (Upper Jurassic) (Late Jurassic)
Highly sheared graywacke, mudstone, siltstone, and shale with lenses and pods of sheared greenstone, limestone, chert, blueschist, and serpentine. Identified as melange by some investigators
Sedimentary and volcanic rocks, partly metamorphosed (Triassic and Permian) (Permian to Triassic)
Complexly folded, locally highly foliated and recrystallized undifferentiated sedimentary and volcanic rocks that in places are lithologically similar to Jurassic and Triassic rocks in the Aldrich Mountains of the Blue Mountains province and in other places resemble Elkhorn Ridge Argillite, Clover Creek Greenstone, and Burnt River Schist (Gilluly, 1937). Age probably mostly Late Permian to Late Triassic, but, as shown, may include some Early Jurassic rocks
Rhode Island
Blackstone Group - greenstone, amphibolite, serpentinite (Late Proterozoic? or older?)
Blackstone Group - greenstone, amphibolite, serpentinite - Dark-green, massive to foliated metamorphosed gabbroic and basaltic rock interlayered with epiclastic rock; local pillow-structures preserved. Consists primarily of epidote, actinolite, chlorite, and plagioclase. Includes rock mapped formerly as Hunting Hill Greenstone.
South Carolina
Latimer complex of Griffin (1979) (Paleozoic or Neoproterozoic)
Latimer complex of Griffin (1979): metamorphosed mafic-ultramafic complex consisting mainly of mafic rocks including amphibolite, metagabbro, and greenstone metabasalt
South Dakota
Metabasalt (Proterozoic | Paleoproterozoic)
Dark-green amphibolite, actinolite schist, and greenstone. Interflow units consists of graphitic schist, chert, and carbonate- and silicate-facies iron-formation. Thickness of individual flows 50-400 ft (244-1,524 m).
Metagabbro (Proterozoic | Paleoproterozoic)
Dark-green sills of amphibolite, actinolite schist, greenstone, and serpentine. Thickness of sills variable, up to 1,000 ft (305 m).
Virginia
Garrisonville Mafic Complex (Proterozoic Z-Cambrian)
Garrisonville Mafic Complex - Metamorphosed mafic and ultramafic rocks
Georgetown Intrusive Suite (Cambrian)
Georgetown Intrusive Suite - Tonalite, quartz gabbro, quartz diorite, metapyroxenite, and hornblendite.
Metaperidotite, Metapyroxenite, and Hornblende Metagabbro (Proterozoic Y)
Metaperidotite, Metapyroxenite, and Hornblende Metagabbro - Serpentinite is metaperidotite, Hornblende metagabbro
Metavolcanic and Metasedimentary Rocks - Greenstone or amphibole gneiss. (Cambrian)
Metavolcanic and Metasedimentary Rocks - Greenstone or amphibole gneiss.
Mount Rogers Formation - Conglomerate, graywacke, laminated siltstone, and shale. (Proterozoic Z)
Mount Rogers Formation - Conglomerate, graywacke, laminated siltstone, and shale.
Mount Rogers Formation - Greenstone with interbedded sedimentary rocks (Proterozoic Z)
Mount Rogers Formation - Greenstone with sedimentary interbeds.
Virgilina Greenstone (Proterozoic Z)
Virgilina Greenstone - Greenstone metabasalt.
Vermont
Ammonoosuc Volcanics (Ordovician)
Ammonoosuc Volcanics - Fine-grained chloritic and biotitic gneiss and greenstone in areas north of Bellows Falls; biotite gneiss and amphibolite south of Bellows Falls. (Southeastern Vermont).
Hazens Notch Formation, Belvidere Mountain Amphibolite Member (Cambrian)
Hazens Notch Formation, Belvidere Mountain Amphibolite Member - Coarse- to fine-grained hornblende-epidote-albite rock; grades to epidote-chlorite-actinolite-albite greenstone where less metamorphosed. (Northern and Central Vermont).
Hazens Notch Formation, Greenstone and Amphibolite (Cambrian)
Hazens Notch Formation, Greenstone and Amphibolite - Chiefly albite-actinolite-chlorite-epidote greenstone; locally hornblende-epidote-chlorite-albite amphibolite. (Northern and Central Vermont).
Hoosac Formation, Amphibolite and Greenstone (Cambrian)
Hoosac Formation, Amphibolite and Greenstone - Amphibolite and actinolitic greenstone. (Southern and Central Vermont).
Hoosac Formation, Turkey Mountain Member (Cambrian)
Hoosac Formation, Turkey Mountain Member - Amphibolite and actinolitic greenstone characterized by oval, 1/8 to 3/8 inch spots, chiefly of epidote. (Southern and Central Vermont). Discontinuous lenses of metabasalt, informally referred to as Turkey Mountain metabasalt member of Hoosac Formation, actually occur at different stratigraphic positions extending through a stratigraphic distance of 100 to 400 m above base of Hoosac Formation. From type area on Turkey Mountain in Saxtons River quad south to Massachusetts State line, basalts form at least three relatively persistent units (Ratcliffe, 1991). Basalt mapped in northeast corner of this map, above Wilmington thrust system, correlates with type Turkey Mountain. As used here, Turkey Mountain metabasalt member consists of several laterally and vertically discontinuous, nonidentical flows and volcaniclastic deposits including, but not restricted to, type Turkey Mountain Member of Hoosac Formation as used by Doll and others (1961) and by Skehan (1961). They mapped the lower basalts as unnamed greenstones in Hoosac Formation. Turkey Mountain metabasalt member consists of light-green to dark-green epidote-amphibole greenstones and amphibolite metabasalts. Metabasalt varies from massive to very well layered. Finely laminated, quartzose and epidotitic volcaniclastic beds several centimeters thick are interlayered with more massive, strongly foliated, black amphibolite. Where in contact with surrounding metasedimentary rocks, layering within metabasalt and volcaniclastic beds is concordant and gradational with enclosing metasediment. Light-gray or yellowish-greenish-gray, well-laminated quartzite or, less commonly, gritty, pebbly conglomerate 0.5 to 5 m thick marks upper contact with unnamed granofels member of Hoosac Formation. Base of Turkey Mountain metabasalt member in contact with rusty muscovite-albite-biotite schist. Metabasalts probably originated as thin composite basalt lava flows that contained intercalated basaltic volcaniclastic rocks. Age is Late Proterozoic and Early Cambrian (Ratcliffe, 1993).
Missisquoi Formation, Coburn Hill Volcanic Member (Ordovician)
Missisquoi Formation, Coburn Hill Volcanic Member - Actinolite-epidote-chlorite-albite greenstone and hornblende-albite-epidote amphibolite; includes pillow lavas.
Orfordville Formation, Post Pond Volcanics (Ordovician)
Orfordville Formation, Post Pond Volcanics - Greenstone, green chloritic schist interbedded with schistose felsite, quartz-feldspar-sericite schist; fine-grained chloritic, biotitic gneiss, all west of Ammonoosuc fault; mainly amphibolite east of the Ammonoosuc fault.
Orfordville Formation, Sunday Mountain Volcanics (Ordovician)
Orfordville Formation, Sunday Mountain Volcanics - Greenstone, chloritic schist, felsite, and quartz-feldspar-sericite schist.
Ottauquechee Formation, Greenstone and Amphibolite (Cambrian)
Ottauquechee Formation, Greenstone and Amphibolite. The Ottauquechee contains two major units: A black phyllite and the Thatcher Brook Member. The black phyllite contains a previously unreported sub-unit of gray carbonate schist. The Thatcher Brook Member (named in an abstract by Armstrong and others, 1988) is a carbonaceous albitic schist with greenstones and ultramafics. These rocks have previously been included in the Ottauquechee but have never been differentiated from the black phyllite. Member is in fault contact with the silvery green schist of the Pinney Hollow Formation to the west. Age is Cambrian (Ratcliff, in press).
Pinnacle Formation, Tibbit Hill Volcanic Member (Cambrian)
Pinnacle Formation, Tibbit Hill Volcanic Member - Albite-actinolite-chlorite-epidote greenstone; locally pillowed and vesicular. (Northern and Central Vermont).
Pinney Hollow Formation, Chester Amphibolite Member (Cambrian)
Pinney Hollow Formation, Chester Amphibolite Member - Thin-layered, ligniform amphibolite and hornblende schist; includes actinolitic greenstone and greenstone north of Windham. (Southern and Central Vermont).
Pinney Hollow Formation, Greenstone (Cambrian)
Pinney Hollow Formation, Greenstone - Greenstone and actinolitic greenstone. (Southern and Central Vermont).
Shaw Mountain Formation (Silurian)
Shaw Mountain Formation - Chiefly tan to brown weathered quartzose limestone and calcareous quartzite characterized by specks of limonite after ankerite; locally underlain by quartz conglomerate and overlain by blue fossiliferous crystalline limestone; greenstone and quartz-sericite schist.
Stowe Formation, greenstone and amphibolite (Cambrian-Ordovician)
Stowe Formation, greenstone and amphibolite - Epidote-albite-chlorite rocks contain actinolite and hornblende where more metamorphosed.
Underhill Formation, Greenstone (Cambrian)
Underhill Formation, Greenstone - varied composition including albite-chlorite-epidote-calcite and sericite-magnetite-chlorite-clinozoisite rocks. (Northern and Central Vermont).
Underhill Formation, Peaked Mountain Member (Cambrian)
Underhill Formation, Peaked Mountain Member - Greenstone. (Northern and Central Vermont).
Waits River formation, Standing Pond Volcanic Member (Devonian)
Waits River formation, Standing Pond Volcanic Member - Amphibolite, garnet amphibolite, coarse garnet schist with fasciculitic hornblende, and hornblende maculite; contains pillow lavas near St. Johnsbury and passes eastward into actinolitic greenstone and greenstone south of Windsor.
Washington
Carboniferous and Permian volcanic rocks (Devonian to Permian; Triassic in Asotin County)
Predominantly altered andesite, basalt, and diabase with interbedded chert and argillite; includes some tuff, greenstone, and spilitic volcanic rocks; northern Cascade Mountains. Mostly schistose greenstone, some agglomerate, and rarely lapilli; includes minor beds of limestone with associated argillite and graywacke; northwestern Stevens County.
Carboniferous-Permian sedimentary and volcanic rocks (Devonian to Permian; some Jurassic)
Sedimentary and volcanic rocks, undivided. Cherty and slaty argillite, siltstone, graywacke, chert, greenstone, tuff, andesite, and spilitic volcanics.
Mesozoic-Tertiary volcanic rocks, undivided (Oligocene to Eocene)
Altered basalt, pillow lavas, and flow breccia of inner volcanic belt of Olympic Peninsula; includes minor interbedded red limy argillite and associated manganese ore.
Ordovician rocks (Middle Ordovician)
Mainly black to gray slate or slaty argillite, argillite, black to dark-gray siltstone in north-central Stevens County and grayish olive-green silty argillite in west-central Stevens County. Many occurrences of Early and Middle Ordovician graptolites; also rare conodonts.
Permian rocks (Permian-Triassic)
Conglomerate, graywacke, siltstone, argillite and interbedded fossiliferous limestone, greenstone, and minor angular conglomerate in northwestern Stevens and Ferry Counties. Impure quartzite, sandstone, graywacke, greenstone, ribbon chert, chert breccia, and limestone in Snohomish County and on San Juan Island. Lower Permian limestone on Black Mountain in northwestern Whatcom County. Middle Permian rocks in northeastern Washington.
Precambrian conglomerate (Late-Proterozoic)
Gray-brown, coarse, poorly sorted pebbles and cobbles of limestone, dolomite, reddish-brown quartzite, black slate or phyllite, and rarely granitic rocks in a gray sandy phyllite matrix; northeastern Pend Oreille County and southwestern Stevens County. Rocks become finer grained and more schistose and the unit becomes thicker toward the southwest, where there is included an isolated subunit which may be a tillite, consisting of cobbles, boulders, and blocks of argillite and carbonate rocks in a fine silty matrix.
Precambrian (?) phyllite (Cambrian-Precambrian boundary)
Mostly phyllite with interbedded carbonate rocks, quartzite, and gritstone; some tufflike beds and conglomerate at the base. Rocks confined to northeastern Pend Oreille County and central Stevens County.
Precambrian volcanic rocks (Late-Proterozoic)
Mostly homogenous schistose greenstone; in places massive, mottled, and containing conspicuous calcite and epidote. Tuffaceous chlorite schist in upper part in northern Pend Oreille County. Amphibolite and plagioclase amphibolite in Little Pend Oreille Lakes district. Massive to sheared or schistose greenstone with dark-green ovoid spots; agglomeratic and amygodaloidal in places; sheared pillows near Blue Creek, central Stevens County; minor intrusive phase and probable center of eruption west of Finch magnesite quarry; central to southwestern Stevens County.
Pre-Middle Jurassic sedimentary and volcanic rocks (Jurassic)
Predominantly sedimentary rocks. Graywacke, argillite, and slate; includes minor marble, siltstone, arkose, conglomerate, ribbon cherts, and volcanic rocks.
Pre-Middle Jurassic volcanic rocks, undivided (Early Cretaceous-Late Jurassic)
Predominantly greenstone and spilitic volcanic rocks; includes some slate, argillite, and graywacke.
Pre-Tertiary basic intrusive rocks (Triassic-Permian)
Predominantly gabbro and metagabbro; includes hornblendite, peridotite, and pyroxenite. In Nighthawk district and near 49th Parallel in Okanogan County and in Orient district of Stevens County.
Pre-Tertiary metamorphic rocks, undivided (Probably Permian)
Schist, gneiss, marble, quartzite, amphibolite, greenstone, metaconglomerate, graywacke; includes metasedimentary, volcanic, and intrusive rocks. Some areas, as on San Juan Islands, show little if any metamorphism.
Pre-Tertiary sedimentary and metasedimentary rocks, undivided (Mostly Early Cretaceous to Middle Jurassic, possibly includes minor Eocene rocks)
Graywacke, argillite, phyllite, chert, talc, and graphite schist; some faulted-in blocks of serpentinite and greenstone. Includes minor limestone on San Juan Island.
Pre-Tertiary ultrabasic intrusive rocks (Late-Jurassic)
Peridotite and pyroxenite; generally altered partly or completely to serpentine. Includes serpentinite and saxonite on Sumas Mountain, Whatcom County.
Pre-Tertiary volcanic rocks, undivided (Probably mostly Jurassic)
Andesite and basalt flows, and greenstone; includes minor interbedded limestone, arkose, quartzite, and chert beds.
Pre-upper Eocene rocks (Eocene (Olympic Peninsula); Cretaceous(?) (Yakima County))
Argillite and graywacke between inner and outer volcanic belts in Olympic Peninsula. Sheared carbonaceous argillite, argillite, graywacke, and minor conglomerate lenses and altered lava flows in western Yakima County.
Pre-Upper Jurassic metamorphic rocks of the low-grade zone (Jurassic)
Greenschist, phyllite, and slate; includes some limestone, quartzose phyllite, schistose metaconglomerate, breccia, and basic igneous rocks. Includes schist locally.
Tertiary-Cretaceous basic intrusive rocks (Cretaceous-Jurassic)
Diorite and gabbro in western Snohomish County.
Triassic sedimentary rocks, undivided (Triassic with Permian where impossible to differentiate)
Predominantly limestone, marble, and dolomite near Riverside in Okanogan County. Conglomerate, shale, graywacke, gritstone, and limestone on San Juan Island. Siltstone with greenstone locally on Orcas Island. Graywacke conglomerate, cherty greenstone, and limestone in northern Ferry County.
Upper Jurassic-Lower Cretaceous sedimentary and volcanic rocks (Late Cretaceous-Jurassic)
Sedimentary and volcanic rocks, undivided. Graywacke, argillite, siltstone, slate, volcanic rocks, phyllite, greenschist, and greenstone.
Upper Jurassic-Lower Cretaceous sedimentary and volcanic rocks (Late Jurassic-Early Cretaceous)
Predominantly sedimentary rocks. Graywacke, argillite, and siltstone with some slate and phyllite; includes graywacke breccia and ribbon chert with minor local limestone lenses and basalt flows.
Upper Paleozoic rocks, undivided (Ordovician)
Mostly graywacke, interbedded quartzite and phyllite, greenstone and serpentine, and black shale with minor limestone. Some quartz-mica schist in Bald Knob area of Ferry County. Schist, gneiss, and amphibolite in other parts of Ferry County. Some rocks of lower Paleozoic age, possibly Precambrian, and Mesozoic may be included.
West Virginia
Catoctin Formation (Cambrian/Precambrian)
Catoctin Formation - predominantly a greenstone. Basic lava flows, schist and gneiss, containing chlorite, plagioclase, amphibolite, and epidote. Includes minor quantities of arkose and thin clastics. Western subsurface extension presently unknown.

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