Likely basalt (possibly a dark beach pebble)
Basalt; fine-grained mafic volcanic rock composed mainly of plagioclase and pyroxene, commonly with olivine
igneous
Category
Man Made Rock (Technosol)
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Limestone
Calcareous sedimentary rock (CaCO3)
sedimentary
Moss-covered Limestone with Quartz/Calcite Pocket
Calcium Carbonate (CaCO3) rock with biological moss coating
sedimentary
Quartzite Pebble
Quartzite (SiO2)
metamorphic
Vesicular Basalt (Scoria)
Vesicular Basalt
igneous
Porphyritic Basalt (Flowerstone)
Porphyritic Basalt (Mafic volcanic rock)
igneous
Sandstone
Arenite (SiO2 dominant)
sedimentary
Sandstone
Arenite (composed primarily of SiO2)
sedimentary
Sandstone (Graywacke)
Clastic Sedimentary Rock (Lithic Sandstone)
sedimentary
Basalt
Basalt (Mafic volcanic rock)
igneous
Pyrite Schist
Metamorphic rock containing FeS2 (Pyrite) with mica and quartz
metamorphic
Lapis Lazuli
(Na,Ca)8(AlSiO4)6(S,SO4,Cl)1-2 (Complex silicate rock)
metamorphic
River Pebble / Quartzite Rock
Metamorphic Quartzite (primarily SiO2)
metamorphic
Sandstone (Ferruginous)
Arenite with Iron Oxide matrix
sedimentary
Basalt with Epidote (Porphyritic Basalt)
Mafic Porphyritic Basalt with (Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)) inclusions
igneous
River Pebble (Quartzite)
Quartzite (SiO2)
metamorphic
Chalcedony in Limestone Host Rock
Silicon Dioxide (SiO2) within Calcium Carbonate (CaCO3)
Mineral within Sedimentary Rock
Sandstone
Clastic sedimentary rock (Quartz arenite)
sedimentary
Unakite
Unakite (Altered Granite composed of Orthoclase KAlSi3O8, Epidote Ca2(Al, Fe)3(SiO4)3(OH), and Quartz SiO2)
metamorphic
Quartz Druzy on Matrix
Silicon Dioxide (SiO2)
mineral
Sandstone
Arenite (Quartz Sandstone)
sedimentary
Granite
Granite
igneous
Basalt
Basalt (Mafic Extrusive Igneous Rock)
igneous
Basalt
Extrusive mafic igneous rock
igneous
Slate
Foliated Metamorphic Rock
metamorphic
Polygenetic Conglomerate (or Breccia)
Clastic Sedimentary Rock
sedimentary
Unakite
Epidotized Granite
metamorphic
Granite
Plutonic felsic igneous rock
igneous
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone
Arenite (SiO2 principal)
sedimentary
Granite
Granite (composed primarily of Quartz, Feldspar, and Mica/Amphibole)
igneous
River Pebble (Basalt or Gabbro)
Mafic Igneous Rock
igneous
Rounded pebble, likely granite or granitic gneiss
Granite: quartz + feldspar + mica; the specimen may be a granitic metamorphic variant
igneous
Sandstone (River Cobble)
Clastic Sedimentary Rock (primarily Quartz with Feldspar)
sedimentary
Cockle Shell (Fossil or Recent)
Class Bivalvia, Family Cardiidae (e.g., Cerastoderma edule for common cockle)
Sedimentary (Biogenic, a type of fossil)
Sandstone
Clastic sedimentary rock (primarily SiO2)
sedimentary
Jasper
Microcrystalline Quartz (SiO2)
sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
gemstone
Quartz Pebble
Silicon Dioxide (SiO2)
sedimentary
Copper Ore (Malachite and Azurite on Host Rock)
Cuprite, Malachite, and Azurite dissemination in gangue
mineral
Jasper
Silicon Dioxide (Microcrystalline Quartz, SiO2)
sedimentary
Quartz
Silicon Dioxide (SiO2)
mineral