Mineral_rock

Geode (Unopened)

Crystalline Quartz or Chalcedony filled Geode (SiO2)

Sandstone

Clastic sedimentary rock (primarily SiO2)

Sandstone

Arenite (SiO2 principal)

Sandstone (Greywacke/Siltstone variant)

Arenite / Wacke (SiO2 with diverse mineral inclusions)

Sandstone

Arenite (SiO2 based)

Sandstone

Arenite (SiO2 based)

Sandstone

Arenite (SiO2 dominant)

Lapis Lazuli (polished cabochon/sphere)

Na8[Al6Si6O24]Sn with accessory minerals (Pyrite, Calcite)

Hag Stone

Perforated sedimentary rock (typically flint, chert, or limestone)

Decorative polished pebbles

Likely mixed quartz-rich lithologies, including quartzite, jasper, and/or basalt

Dark green metamorphic rock, likely serpentinite

Serpentinite, composed mainly of serpentine-group minerals (antigorite, lizardite, or chrysotile), commonly with magnetite and minor chlorite/talc

Pegmatitic pink feldspar–quartz rock

Granitic pegmatite; chiefly microcline/orthoclase feldspar (KAlSi₃O₈), quartz (SiO₂), and minor mica

Weathered quartz-rich rock, likely quartzite or altered sandstone

Quartzite (mostly microcrystalline quartz, SiO₂); exact identification is uncertain from the photograph

Serpentinite

Serpentinite (Hydrated magnesium iron phyllosilicate)

Garnet-bearing Schist / Conglomerate Specimen

Metamorphic rock with almandine garnet porphyroblasts

Plume Agate or Moss Agate

Agate (SiO2)

Porphyritic Basalt

Porphyritic Basalt with Olivine phenocrysts

Dalmatian Jasper / Dalmatian Stone

Peralkaline Rock (Silicon Dioxide with Amphibole inclusions)

Serpentine

Antigorite, Lizardite, or Chrysotile (Mg, Fe)3Si2O5(OH)4

Weathered banded sandstone pebble

Quartz-rich sandstone (predominantly SiO₂)

Granite and Mixed Landscape Gravel

Plutonic Igneous Rock / Weathered Alluvium

Weathered River Rock (likely Chert or Basalt with algae)

Silicon dioxide (SiO2) with organic biofilm

Red Sandstone

Arenite (with Iron Oxide / Hematite cementation)

Common Pebble / Sedimentary Rock Fragment

Lithified clastic sediment

Emerald

Beryl (Be3Al2(SiO3)6)

Goethite pseudomorph after Pyrite

Goethite (FeO(OH)) pseudomorph after Pyrite (FeS2)

Tumbled quartz (likely milky quartz)

Quartz, silicon dioxide (SiO₂)

Given the appearance, it's likely a fragment of an igneous or metamorphic rock composed of multiple minerals. Without specific diagnostic features, it's difficult to give a common name other than 'crystalline rock fragment'. If pressed to guess based on the granular, somewhat light and dark speckled appearance, it could be a fragment of granite or a related intrusive igneous rock.

As a rock fragment, it does not have a single scientific mineral name; rather, it's a piece of a rock which is a combination of minerals. If it were granite, its main mineral composition would be quartz (SiO2), feldspar (e.g., KAlSi3O8 - orthoclase, (Na,Ca)(Al,Si)4O8 - plagioclase), and mica (e.g., KAl2(AlSi3O10)(OH)2 - muscovite or K(Mg,Fe)3AlSi3O10(OH)2 - biotite), among others.

Milky Quartz

Silicon Dioxide (SiO2)

Limonite and Goethite Iron Ore

Hydrated Iron Oxide Hydroxide (FeO(OH)·nH2O)

Chalcedony (Agate nodule fragment)

Silicon Dioxide (SiO2)

Milky Quartz

Quartz (Silicon Dioxide - SiO2)

Peacock Ore (Bornite or Chalcopyrite)

Bornite (Cu5FeS4) or Acid-Washed Chalcopyrite (CuFeS2)

Weathered banded metamorphic rock, likely gneiss

Banded gneiss; commonly quartz–feldspar–mica assemblage

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Dark gray igneous rock, likely basalt

Basalt; fine-grained plagioclase–pyroxene rock, commonly with minor olivine and magnetite

Banded gneiss

Gneiss, chiefly quartz–feldspar–mica (variable composition)

Malachite

Copper Carbonate Hydroxide, Cu2CO3(OH)2

Pyrite in Matrix

Iron Disulfide (FeS2)

Lepidolite

K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2

Hematite

Iron(III) oxide (Fe2O3)

Carnelian

Carnelian (SiO2 with Iron Oxide impurities)