mafic

Obsidian 36
by James St. John

Black porphyritic dacite (upper Holocene, 14 May 1915; Devastated Area, Lassen Volcano National Park, California, USA) 1
by James St. John

Obsidian 28
by James St. John

Obsidian 27
by James St. John

Cripple Creek Diatreme (Early Oligocene, 32 Ma; Cresson Pit, Cripple Creek Mining District, Colorado, USA) 38
by James St. John

Narrows Basalt (Lower Pleistocene, 1.5-1.6 Ma) (Narrows of the Yellowstone River, northeastern Yellowstone National Park, Wyoming, USA) 3
by James St. John

Basaltic effusive eruption (early evening, 9 December 2022) (“Fissure 3”, Northeast Rift Zone, Mauna Loa Volcano, Hawaii)
by James St. John

Fluorite vein (Cripple Creek Diatreme, Early Oligocene, 32 Ma; Cresson Pit, Cripple Creek Mining District, Colorado, USA) 9
by James St. John

Columnar-jointed rhyolitic obsidian lava flow (Roaring Mountain Member, Plateau Rhyolite, Upper Pleistocene, ~59 ka; Obsidian Cliff, Yellowstone, Wyoming, USA) 33
by James St. John

Polymetallic massive sulfide (Middle Tholeiitic Unit, Kidd-Munro Assemblage, Neoarchean, 2.711 to 2.719 Ga; drill cores at the Potter Mine, east of Timmins, Ontario, Canada) 41
by James St. John

Gabbro (Duluth Complex, Mesoproterozoic, 1099 Ma; Rt. 1 roadcut between Heart Lake & Little Spring Lake, Minnesota, USA) 6
by James St. John

Metamorphosed pillow basalt (Ely Greenstone, Neoarchean, ~2.722 Ga; large glacial erratic along Main Street, Ely, Minnesota, USA) 12
by James St. John

Verde Lavras Granite (orthogneiss, Paleoproterozoic, 1.9 Ga; Lavras, Minas Gerais State, Brazil)
by James St. John

Columnar-jointed basalt (Columbia River Flood Basalt, Miocene, ~15-17 Ma; Mud Hollow, Oregon, USA) 19
by James St. John

Metamorphosed pillow basalt (Ely Greenstone, Neoarchean, ~2.722 Ga; large loose block at Ely visitor center, Ely, Minnesota, USA) 2
by James St. John

Porphyritic phonolite (Cripple Creek Diatreme, Early Oligocene, 32 Ma; Ironclad area, Cripple Creek Mining District, Colorado, USA) 2
by James St. John

Porphyritic granite (Giants Range Batholith, Neoarchean, 2.67-2.68 Ga; Rt. 1 roadcut north of the South Kawishiwi River, Minnesota, USA) 12
by James St. John

Metamorphosed pillow basalt (Ely Greenstone, Neoarchean, ~2.722 Ga; large loose block at Ely visitor center, Ely, Minnesota, USA) 11
by James St. John

Metamorphosed pillow basalt (Ely Greenstone, Neoarchean, ~2.722 Ga; large glacial erratic along Main Street, Ely, Minnesota, USA) 4
by James St. John

Cripple Creek Diatreme (Early Oligocene, 32 Ma; Cresson Pit, Cripple Creek Mining District, Colorado, USA) 35
by James St. John

Snowflake obsidian 4
by James St. John

Platinum-palladium ore (Johns-Manville Reef, Stillwater Complex, Neoarchean, 2.71 Ga; Stillwater Mine, Beartooth Mountains, Montana, USA) 4
by James St. John

Fluorite vein (Cripple Creek Diatreme, Early Oligocene, 32 Ma; Cresson Pit, Cripple Creek Mining District, Colorado, USA) 7
by James St. John

Metakomatiite lava flows (Upper Komatiitic Unit, Kidd-Munro Assemblage, Neoarchean, 2.711-2.719 Ga; Pyke Hill, near the Potter Mine, east of Timmins, Ontario, Canada) 54
by James St. John

Olivine diabase (Lafayette Bluff Sill, Proterozoic; Lafayette Bluff Tunnel, northeastern Minnesota, USA) 6
by James St. John

Fluorite vein (Cripple Creek Diatreme, Early Oligocene, 32 Ma; Cresson Pit, Cripple Creek Mining District, Colorado, USA) 8
by James St. John

Olivine diabase (Lafayette Bluff Sill, Proterozoic; Lafayette Bluff Tunnel, northeastern Minnesota, USA) 8
by James St. John

Brown scoria
by James St. John

Peperite (Middle Tholeiitic Unit, Kidd-Munro Assemblage, Neoarchean, 2.711-2.719 Ga; just southwest of the Potter Mine, east of Timmins, Ontario, Canada) 4
by James St. John

Pentlandite in pyrrhotite (late Paleoproterozoic, 1.85 Ga; South Mine, Sudbury Impact Crater, Ontario, Canada) 2
by James St. John

Chromitite (Stillwater Complex, Neoarchean, 2.71 Ga; Beartooth Mountains, Montana, USA) 3
by James St. John

Chaos Crags volcanic domes & Chaos Jumbles Landslide (Holocene; Lassen Volcano National Park, California, USA) 2
by James St. John

Metakomatiites (Upper Komatiitic Unit, Kidd-Munro Assemblage, Neoarchean, 2.711-2.719 Ga; Pyke Hill, near the Potter Mine, east of Timmins, Ontario, Canada) 5
by James St. John

Cripple Creek Diatreme (Early Oligocene, 32 Ma; Cresson Pit, Cripple Creek Mining District, Colorado, USA) 29
by James St. John

Mafic dike Sennett Hole Geology hike West Point on the Eno Durham NC 5901
by bobistraveling

Metakomatiites (Upper Komatiitic Unit, Kidd-Munro Assemblage, Neoarchean, 2.711-2.719 Ga; Pyke Hill, near the Potter Mine, east of Timmins, Ontario, Canada) 3
by James St. John

"Rockville White Granite" (porphyritic granite, Rockville Granite, late Paleoproterozoic, 1.73 to 1.78 Ga; quarry near Rockville, Minnesota, USA) 3
by James St. John

Bronzitic anorthosite (Stillwater Complex, Neoarchean, 2.71 Ga; mine core dump, Stillwater Mine, Beartooth Mountains, Montana, USA) 1
by James St. John

Metamorphosed pillow basalt (Ely Greenstone, Neoarchean, ~2.722 Ga; large glacial erratic along Main Street, Ely, Minnesota, USA) 11
by James St. John

Sulfidic anorthosite (platinum-palladium ore) (Johns-Manville Reef, Stillwater Complex, Neoarchean, 2.71 Ga; Stillwater Mine, Beartooth Mountains, Montana, USA) 6
by James St. John

Polymetallic massive sulfide (Middle Tholeiitic Unit, Kidd-Munro Assemblage, Neoarchean, 2.711 to 2.719 Ga; Potter Mine, east of Timmins, Ontario, Canada) 3
by James St. John

Porphyritic phonolite (Cripple Creek Diatreme, Early Oligocene, 32 Ma; Ironclad area, Cripple Creek Mining District, Colorado, USA) 1
by James St. John

Black porphyritic dacite (upper Holocene, 14 May 1915; Devastated Area, Lassen Volcano National Park, California, USA) 14
by James St. John

Platinum-palladium ore (Johns-Manville Reef, Stillwater Complex, Neoarchean, 2.71 Ga; Stillwater Mine, Beartooth Mountains, Montana, USA) 7
by James St. John

Metamorphosed pillow basalt (Ely Greenstone, Neoarchean, ~2.722 Ga; large loose block at Ely visitor center, Ely, Minnesota, USA) 12
by James St. John

Cripple Creek Diatreme (Early Oligocene, 32 Ma; Cresson Pit, Cripple Creek Mining District, Colorado, USA) 33
by James St. John

Marinace Green Granite (polymict metaconglomerate) (Ouricuri do Ouro Formation, Mesoproterozoic, ~1.6-1.7 Ga; Bahia, Brazil) 10
by James St. John

Chromitite (Stillwater Complex, Neoarchean, 2.71 Ga; Beartooth Mountains, Montana, USA) 2
by James St. John

Metamorphosed pillow basalt (Ely Greenstone, Neoarchean, ~2.722 Ga; large glacial erratic along Main Street, Ely, Minnesota, USA) 9
by James St. John

Basalt (Lintz, Germany) 1
by James St. John

Scheelite-pyroxene-chalcopyrite-pyrite skarn (Chorukh-Dairon Deposit, Late Pennsylvanian to earliest Permian, ~298-306 Ma; Chorukh-Dairon Mine, Tajikistan) 1
by James St. John

Metamorphosed pillow basalt (Ely Greenstone, Neoarchean, ~2.722 Ga; large glacial erratic along Main Street, Ely, Minnesota, USA) 10
by James St. John

Sulfidic anorthosite (platinum-palladium ore) (Johns-Manville Reef, Stillwater Complex, Neoarchean, 2.71 Ga; Stillwater Mine, Beartooth Mountains, Montana, USA) 16
by James St. John

Large bronzite crystal in bronzitic anorthosite (Stillwater Complex, Neoarchean, 2.71 Ga; mine core dump, Stillwater Mine, Beartooth Mountains, Montana, USA) 2
by James St. John

Cinder cone volcano (Quaternary; Inferno Crater, Craters of the Moon Lava Field, Idaho, USA) 7
by James St. John

"Missouri Red Granite" (Graniteville Granite, Mesoproterozoic, 1.317 Ga; St. Francois Mountains, Missouri, USA)
by James St. John

Red Cone (Late Pleistocene cinder cone with basaltic andesite, 35-36 ka; northwest of Crater Lake Caldera, Oregon, USA) 7
by James St. John

Red Cone (Late Pleistocene cinder cone with basaltic andesite, 35-36 ka; northwest of Crater Lake Caldera, Oregon, USA) 6
by James St. John

Obsidian 17
by James St. John

Polymetallic massive sulfide (Middle Tholeiitic Unit, Kidd-Munro Assemblage, Neoarchean, 2.711 to 2.719 Ga; drill core at the Potter Mine, east of Timmins, Ontario, Canada) 25
by James St. John