Obradovicite

Comments: Brownish yellow obradovicite coatings on quartz.
Location: Chuquicamata, Antofagasta, Chile. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Offretite

Comments: Clear crystal of offretite on matrix.
Location: Mont Simiouse, near Montbrison, Loire, France. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Ogdensburgite

Comments: Reddish-brown, massive ogdensburgite.
Location: Ogdensburg, Franklin Mining District, Sussex Co., New Jersey, USA. Scale: Picture size 6 mm.
© Thomas Witzke / Abraxas-Verlag

Ohmilite

Comments: Pale yellow translucent acicular ohmilite crystal cluster in matrix.
Location: Hashidate, Ohmi cho, Niigata, Japan. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Ojuelaite

Comments: Yellow-green ojuelaite masses on limonite and quartz.
Location: Mina Ojuela, Mapimi, Durango, Mexico. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Okanoganite-(Y)

Comments: Cream-colored twinned crystal of okanoganite-(Y) on matrix.
Location: Washington Pass, Okanogan County, Washington, USA. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Okenite

Comments: Cotton-ball cluster of white okenite crystals.
Location: Khandivali quarry, Maharashtra, India. Scale: 3x3x2 cm.
© John Betts - Fine Minerals

Oldhamite

Comments: Brown crystalline oldhamite grains in anhydrite.
Location: Ronneburg, Thuringen, Germany. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Olenite

Comments: Colorless, boron-rich crystal of Olenite in quartz.
Location: Koralpe, Styria, Austria. Scale: Crystal size 3 cm.
© Andreas Ertl / Institut f?r Mineralogie und Kristallographie

Oligoclase   Plagioclase

Comments: Rectangular cleavage fragment of salmon-orange oligoclase (sunstone) feldspar.
Location: Norway. Scale: 47x30x7 mm.
© John Betts - Fine Minerals

Oligoclase   Plagioclase

Comments: Clear glassy crystalline oligoclase with milky quartz and muscovite.
Location: Bakersville, Mitchell County, North Carolina, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Olivenite

Comments: Dark green crystals of olivenite on matrix.
Location: Majuba Hill mine, Pershing County, Nevada, USA. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Olivenite   Arsenogoyazite

Comments: White micro-botryoids of arsenogoyazite with light green acicular crystal sprays of olivenite and dark green malachite on brown limonite.
Location: Centennial Eureka Mine, Juab County, Utah. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Olivine   Forsterite

Comments: Peridot (Forsterite) recrystallized at the base.
Location: Skardu, Nooristan, Pakistan. Scale: 2.5 x 2.7 cm.
© Fabre Minerals

Olmsteadite

Comments: Dark brown crystals of olmsteadite with jahnsite on siderite.
Location: Big Chief mine, Keystone, Penningtion County, South Dakota, USA. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Olsacherite

Comments: Light yellow crystals of olsacherite up to 2 mm in matrix.
Location: Colquechaca, Potos?, Bolivia. Scale: Picture size 1.5 cm.
© John Veevaert

Olshanskyite   Henmilite

Comments: Milky white olshanskyite hosting crystals of deep blue henmilite to 6 mm across.
Location: Fuka Mine, Bicchu Town, Kawakama Co., Okayama Pref., Japan. Scale: Crystal size 6 mm.
© John Veevaert

Ominelite

Comments: Photomicrograph of thin-section (plain light) of zoned ominelite (omn) with quartz (qtz) and plagioclase (pl) in alkali feldspar. (AmMin 87:163).
Location: Misen River in Tenkawa, Yoshino, Nara Prefecture, Japan. Scale: Grain size 0.6 mm.
© American Mineralogist

Omphacite

Comments: Dark green crystalline omphacite with glaucophane.
Location: Healdsburg, Sonoma County, California, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Onoratoite

Comments: White crystals of onoratoite with a yellow crystal of sulphur.
Location: Cetine di Cotorniano Mine (Cetine Mine; Tafone Mine), Rosia, Siena, Tuscany, Italy. Scale: Picture size 4 mm.
© Thomas Witzke / Abraxas-Verlag

Opal

Comments: Colorful white opal on a sandstone matrix.
Location: Queensland, Australia. Scale: 9 x 6 x 3 cm.
© Isaias Casanova / IC Minerals

Opal

Comments: Section of fossilized tree limb that is now completely replaced by black opal.
Location: Virgin Valley District, Humboldt Co., Nevada, USA. Scale: 20x13x11 mm.
© John Betts - Fine Minerals

Opal   Todorokite

Comments: Dendritic todorokite in white opal.
Location: Brosso Mine, Ivrea, Torino, Piemonte, Italy. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Orcelite

Comments: Bronze micro spherical orcelite coated with greenish zaratite.
Location: Tiebaghi Massif, New Caledonia. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Ordonezite

Comments: Greenish, glassy crystals of ordonezite.
Location: Santin mine, Guanajuato, Mexico. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Oregonite

Comments: Steel gray, altering to brown, rounded oregonite pebble with serpentinite rock.
Location: Josephine Creek, Josephine County, Oregon, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Orickite

Comments: Black and white image of a polished section showing intergrown crystals of orickite in sodalite (dark). (AmMin 68:246).
Location: Mafic alkalic diatreme at Coyote Peak near Orick, Humboldt County, California, USA. Scale: Image size 0.44 mm.
© American Mineralogist

Orientite

Comments: Reddish brown massive orientite with pyrolusite.
Location: Oriente Province, Cuba. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Orlandiite

Comments: White, acicular crystals of orlandiite.
Location: Baccu Locci Mine, Villaputzu, Cagliari Province, Sardinia, Italy. Scale: Picture size 2 mm.
© Thomas Witzke / Abraxas-Verlag

Orlymanite

Comments: Brown crystalline orlymanite with radiating structure, on inesite.
Location: N'Chwaning Mine, Kuruman, Northern Cape Province, South Africa. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Orpheite

Comments: Opaque botryoidal orpheite crust.
Location: Near Valmy, Humboldt County, Nevada, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Orpiment

Comments: Deep orange-colored orpiment crystal aggregate.
Location: Twin Creeks mine, 62 bench, north of Winnemucca, Humboldt County, Nevada. USA. Scale: 6.5 x 5.5 cm.
© Fabre Minerals

Orthochamosite

Comments: Pale green micaceous orthochamosite in quartz.
Location: Near Manggruvan, Sweden. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Orthochrysotile

Comments: Pale tan asbestos fiber (orthochrysotile) vein in rock.
Location: El Dorado Mine, Salt River Canyon, Gila County, Arizona, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Orthoclase   Lorenzenite

Comments: Striated, dark violet crystal of lorenzenite in cream-colored orthoclase.
Location: Khibiny Massif, Kola Peninsula, Russia. Scale: 1.3 x 1.2 cm.
© John Veevaert

Orthoclase

Comments: Carlsbad twinned crystal of orthoclase. Former Mart?n Oliete Fontela collection.
Location: Zarzalejo, Madrid. Scale: 5.2x4.6x2.2 cm.
© Fabre Minerals

Orthoclase

Comments: Gemmy, twinned adularia (orthoclase) specimen on matrix. Former Bally Museum collection.
Location: Rhonegletscher, Switzerland. Scale: Crystal size 3 x 2 cm.
© Fabre Minerals

Orthoericssonite   Ericssonite   Tephroite

Comments: Dark brown ericssonite, intergrown with orthoericssonite, with pink rhodonite, light brown diopside (var. schefferite) and gray tephroite.
Location: Langban, Varmland, Sweden. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Orthominasragrite

Comments: Dark blue, spherical aggregate of orthominasragrite.
Location: Temple Mountain, Emery Co., Utah, USA. Scale: Picture size 1 mm.
© Thomas Witzke / Abraxas-Verlag

Orthoserpierite

Comments: Vivid blue green sheets and coatings of orthoserpierite on matrix.
Location: Galiuro Mt. Copper Creek, Pinal County, Arizona, USA. Scale: 3.0 X 4.4 cm.
© John Veevaert

Osarizawaite

Comments: Light blue micro crystals of osarizawaite and minor azurite filling vugs.
Location: Silver Hill Mine, near Marana, Pinal Co. Arizona, USA. Scale: 3 x 2 cm.
© John Veevaert

Osmium   Cooperite   Vasilite   Vysotskite

Comments: BSE image taken with a SEM of the sulfide-dominant microparagenesis filling a gas vacuole. Cooperite crystal surrounded by Pd-Cu-Pt-S phase (vasilite?), vysotskite and osmium laths (white) in chalcopyrite-bornite matrix (dark). (CanMin 38:1258).
Location: Pustaya River placer deposit, situated within the Koryak-Kamchatka platinum-bearing belt of Alaskan-type intrusions in eastern Russia. Scale: See Image.
© Canadian Mineralogist

Osumilite-(Fe)

Comments: Dark blue crystals of osumilite-(Fe) in matrix.
Location: Cava Fontana, Monte Arci, Cagliari, Sardinia, Italy. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Oswaldpeetersite

Comments: Yellow oswaldpeetersite in matrix.
Location: Jomac Mine, White Canyon,White Canyon District (White Canyon), San Juan Co., Utah, USA. Scale: Picture size 1.2 mm.
© Thomas Witzke / Abraxas-Verlag

Oswaldpeetersite

Comments: Greenish-yellow, acicular, radial-spherical blebs of oswaldpeetersite on matrix.
Location: Jomac Mine, San Juan County, Utah, USA. Scale: Picture size 5 mm.
© Paul M. Schumacher

Ottrelite

Comments: Dark green crystalline ottrelite in quartz.
Location: Vielsalm, Luxembourg, Belgium. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Otwayite

Comments: Pale green botryoidal otwayite on serpentinite rock.
Location: Otway Prospect, Nullagin Plain, Western Australia, Australia. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Oulankaite   Telargpalite   Tulameenite   Chalcopyrite

Comments: Gray long-prismatic crystal of oulankaite with light grayish telargpalite and pale yellowish-white rims of tulameenite in massive yellowish chalcopyrite. Polished section (from microprobe analysis) in reflected light.
Location: Lukkulaisvaara ultrabasic Massif, Olanga (Oulanka) River, Oulanka plutonic complex, Karelia Republic, Northern Region, Russia. Scale: Picture size 0.12 mm.
© Thomas Witzke / Abraxas-Verlag

Owyheeite

Comments: Acicular owyheeite microcrystals in quartz.
Location: Lower Magnolia Mine, Morey District, Nye County, Nevada, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Oxammite

Comments: Pale yellow translucent crystalline granular oxammite.
Location: Petrogale Cave, Western Australia, Australia. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Oxiberaunite

Comments: Red-brown ball of radiating acicular oxiberaunite (eleonorite) microcrystals, on pegmatitic matrix.
Location: LCA Mine, Bessemer City, Gaston County, North Carolina, USA. Scale: Box size 3.18 cm x 3.18 cm.
© Richard Dale / Dale Minerals

Oyelite   Bultfonteinite

Comments: White encrustation of oyelite covering brownish botryoidal bultfonteinite.
Location: N'Chwaning Mine, Kalahari Manganese Field, Northern Cape Province, South Africa. Scale: 2 x 4 cm.
© John Veevaert

Oyelite

Comments: Tufts of white acicular millimetric oyelite crystals on matrix.
Location: N'Chwaning Mine, Kalahari Manganese Field, Northern Cape Province, South Africa. Scale: Picture size 2 cm.
© Minernet