Organic (Geological Interest)

Milky Quartz with Iron Staining

Silicon Dioxide (SiO2)

Quartz (Smoky/Milky variant)

Silicon Dioxide (SiO2)

Ironstone pebble (likely limonite/goethite-rich)

Limonite, a mixture of hydrated iron oxides; commonly dominated by goethite (α-FeO(OH))

Iron-oxide-stained rock, likely limonite/goethite-bearing stone

Limonite (a mixture of hydrated iron oxides, commonly including goethite, FeO(OH)) coating or staining a host rock

Quartz pebble

Quartz, SiO₂; likely a rounded vein-quartz clast

Quartz Vein in Host Rock

Silicon Dioxide (SiO2) in Altered Host Rock

Quartz (Milky or Smoky Quartz)

Silicon Dioxide (SiO2)

Quartz with Iron Oxide Inclusions

SiO2 with Fe2O3 impurities

Fossilized bone fragment

Fossil bone, composed chiefly of carbonate-fluorapatite (bioapatite)

Speckled rounded stone, possibly basalt or diorite

Indeterminate mafic/intermediate igneous rock; likely fine-grained basaltic or dioritic material

Biotite Mica

Biotite (K(Mg,Fe)3(AlSi3O10)(F,OH)2)

Weathered brown rock fragment

Indeterminate; possibly ferruginous sandstone or weathered volcanic rock

Iron-rich concretion or slag-like mineral fragment

Likely limonite/goethite (FeO(OH)·nH₂O), possibly magnetite-bearing material

Milky Quartz with Iron Staining

Silicon Dioxide (SiO2)

Mica-rich rock, likely mica schist

Mica schist, composed chiefly of muscovite and/or biotite with quartz and feldspar

Quartz (likely Chalcedony or Chert)

Silicon Dioxide (SiO2)

Pyritic Sandstone

Clastic Sedimentary Rock (Pyrite-bearing Sandstone)

Horse Chestnut (Buckeye seed)

Aesculus hippocastanum seed

Weathered metallic sulfide-bearing rock, possibly schist or gneiss

Indeterminate; likely mica-rich metamorphic rock with iron sulfides or magnetite

Iron-rich Gossan with Quartz

Limonite and Goethite with Silicon Dioxide (SiO2)

Peridotite

Ultramafic intrusive igneous rock

Gneiss (specifically a Granitic Gneiss)

Gneiss (Composition: Quartz, Feldspar, Mica)

Milky or Greenish Quartz Pebble

Silicon Dioxide (SiO2)

Quartz / Common Quartzite

Silicon Dioxide (SiO2)

Quartz (Grain)

Silicon Dioxide (SiO2)

Soil with Mineral Detritus and Quartz Fragments

Regolith / Silicate Mineral Aggregate

Coarse-grained granite (probable)

Granite, a quartz–feldspar–mica intrusive igneous rock

Pyrite

Iron Disulfide (FeS2)

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Quartz-rich rock fragment, possibly chalcedony or weathered quartz

Silicon dioxide (SiO₂), likely quartz/chalcedony

Red Coral

Corallium rubrum (Calcium Carbonate, CaCO3 with Carotenoid pigments)

Quartz-veined Basalt

Amygdaloidal or Porphyritic Basalt with Silicon Dioxide (SiO2) vein

Iron-rich, vesicular volcanic rock (possibly scoria)

Scoria, likely basaltic; exact identification requires examination and testing

Worked flint/chert artifact

Microcrystalline quartz (chalcedony), SiO₂; likely a knapped flint or chert flake/core fragment

Ironstone Concretion

Siderite or Hematite-bonded Concretion

Black Pearl (Tahitian Pearl)

Aragonite / Calcite (CaCO3) with Conchiolin

Quartz (Iron-Stained)

Silicon Dioxide (SiO2)

Weathered volcanic rock, likely andesite

Andesite (plagioclase–pyroxene volcanic rock), identification tentative

Sandstone (Pebble)

Arenite / Clastic Sedimentary Rock

Quartz vein in iron-stained host rock

Quartz (SiO₂) with iron-oxide staining; host rock uncertain from the image

Likely lateritic ironstone (limonite/goethite-rich)

Goethite, α-FeO(OH), with possible limonite and clay impurities