Not A Geological Specimen

Crinoid Columnal Fossil in Chert

Crinoidea stemming section in Microcrystalline Quartz (SiO2)

Brain Coral Fossil

Family Mussidae or Merulinidae (Order Scleractinia)

Dendritic limestone or marble slab

Manganese-oxide dendrites in carbonate rock, likely calcite (CaCO₃)

Green aventurine cabochon earrings

Aventurine quartz (SiO₂), likely green quartzite with fuchsite mica

Amethyst bead bracelet

Amethyst, purple quartz (SiO₂)

Ironstone Concretion (Moqui Marble)

Iron-oxide Concretion (Hydrated ferric oxide, Fe2O3·nH2O)

Amygdaloidal Basalt

Basalt (with filled vesicles/amygdules)

Basalt

Mafic volcanic rock (primarily plagioclase feldspar and pyroxene)

Goethite / Limonite Concretion

Iron Hydroxide Oxide (FeO(OH))

Banded Gneiss

Gneiss (High-grade Regional Metamorphic Rock)

Kimberlite

Kimberlite (Porphyritic Peridotite)

Weathered schist or gneiss cobble

Foliated silicate rock, likely mica schist or biotite gneiss

Veined quartz-bearing metamorphic rock

Likely quartzite or quartz-veined hornfels; exact identification requires a fresh surface and tests

Weathered iron-rich sandstone or ironstone concretion

Ferruginous sandstone; chiefly quartz (SiO₂) cemented by iron oxides such as hematite (Fe₂O₃) and goethite (FeO(OH))

Granitic Pegmatite

Granitic Pegmatite (principally Quartz, Potassium Feldspar, and Mica)

Weathered iron-rich limestone or calcareous sandstone

Calcite-rich carbonate rock, possibly ferruginous limestone (CaCO₃ with iron oxides)

Iron-rich sandstone (ferruginous sandstone)

Quartz-rich sandstone cemented by iron oxides, chiefly hematite (Fe₂O₃) and/or goethite (FeO(OH))

Limonite

FeO(OH)·nH2O (Hydrated iron oxide)

Mica Schist

Mica Schist (composed mainly of Muscovite / Biotite, Quartz, and Feldspar)

Septarian Nodule (Dragon Stone)

Septarian Concretion (CaCO3 + CaMg(CO3)2 + SiO2)

Fossilized Syringopora Coral (Organ Pipe Coral Fossil)

Syringopora sp. (Class Anthozoa, Order Tabulata)

Rounded river pebble, likely fine-grained sandstone or siltstone

Indeterminate clastic sedimentary rock; possibly quartz-rich sandstone

Chert Nodule in Limestone (Flint in Chalk)

SiO2 (Microcrystalline Quartz) in CaCO3 (Calcite)

Greenschist (or Serpentinite with Manganese Dendrites)

Greenschist facies metamorphic rock

Weathered iron-rich sandstone or ferruginous conglomerate

Quartz-rich sandstone cemented by iron oxides/hydroxides (primarily hematite and goethite)

Moqui Marble (Iron Concretion)

Iron Oxide Concretion (Goethite/Hematite Cemented Sandstone)

Banded Gneiss

Gneiss (High-grade Regional Metamorphic Rock)

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Chalcedony (Botryoidal)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Likely weathered granite or granitic gneiss

Granite/granitic gneiss, composed mainly of quartz, feldspar, and mica; exact identification is uncertain from the photograph

Milky quartz (massive quartz)

Quartz, silicon dioxide (SiO₂)

Weathered sandstone or iron-rich sedimentary fragment

Quartz-rich sandstone, possibly ferruginous sandstone (SiO₂-dominant)

Limonite (Iron Ore)

Limonite (Hydrous iron(III) oxide-hydroxide mixture, FeO(OH)·nH2O)

Diamond cluster ring

Diamond (carbon, C), faceted and set in jewelry

Iron-rich sandstone or weathered ironstone pebble

Ferruginous sandstone; chiefly quartz (SiO₂) cemented or stained by iron oxides/hydroxides such as hematite (Fe₂O₃) and goethite (FeO(OH))

Iron-rich concretion (probable hematite/limonite nodule)

Goethite–hematite concretion; FeO(OH) and Fe₂O₃, possibly with quartz/clay

Banded Iron Formation (Jaspillite)

Banded Iron Formation (BIF)

Granite cobblestone paving

Granite, primarily quartz, feldspar, and mica; likely gray granite or granodiorite

Green Glass Cullet / Recycled Glass

Amorphous Silicon Dioxide (SiO2) with various metal oxides

Weathered iron-rich rock, possibly laterite or limonite-bearing sandstone

Laterite/limonite-rich material; commonly dominated by goethite (FeO(OH)) and hydrated iron oxides

Weathered iron-rich sandstone or conglomeratic sedimentary cobble

Ferruginous sandstone, possibly polymictic conglomerate

Chert / Flint

Silicon Dioxide (SiO2)