Rock (Likely Sedimentary)

Pyrite-bearing rock (iron pyrite)

Pyrite, FeS₂, likely disseminated or massive in a host rock

Weathered fossiliferous limestone or fossil fragment

Indeterminate bioclastic carbonate rock; likely calcite (CaCO₃) with fossil shell material

Sand Dollar Fossil (Echinoidea)

Class Echinoidea (likely order Clypeasteroida), CaCO3 (Calcite)

Chert (Flint)

Chert (Microcrystalline Quartz, SiO2)

Gneiss (specifically a weathered or stream-worn specimen)

Gneiss (Foliated Metamorphic Rock)

Weathered vuggy quartz-rich rock (probable silicified limestone or quartz breccia)

Microcrystalline quartz (SiO₂) with calcite (CaCO₃), iron oxides, and minor clay minerals

Pebble (likely Quartz or Chert)

SiO₂ (Silicon Dioxide) - referring to the likely main mineral composition, Quartz. If it's chert, the scientific name remains SiO₂ with a microcrystalline structure.

Quartz-rich feldspathic rock, likely granite or granitic gneiss

Granite/granitic gneiss; chiefly quartz (SiO₂), feldspar, and minor mica

Fossiliferous Limestone (Crinoidal Limestone)

Biogenic Limestone (Calcium Carbonate, CaCO3)

Not a geological specimen

N/A (man-made object)

Gneiss pebble

Banded gneiss, commonly quartz–feldspar–biotite gneiss

Weathered quartz-rich stone, possibly fossiliferous limestone

Indeterminate; likely calcite-rich limestone (CaCO₃) or weathered quartz-bearing rock

Granite (Dioritic or Hornblende-rich)

Phaneritic Plutonic Felsic to Intermediate Igneous Rock

Conglomerate

Polymictic clast-supported conglomerate, likely ferruginous

Banded Rock (likely Quartz-rich)

Uncertain, likely a Metamorphic Rock (e.g., Gneiss or Schist) with prominent Quartz and other minerals

Iron-Stained Quartzite

Recrystallized Meta-Quartzite (primarily SiO2)

Likely basalt or vesicular volcanic rock

Basalt, possibly scoriaceous basalt; exact identification is uncertain from the photograph

Fossiliferous limestone

Calcarenite/bioclastic limestone, predominantly calcite (CaCO₃)

Weathered quartz-rich rock, possibly granite or quartzite

Indeterminate; likely quartz–feldspar aggregate, possibly granitic gneiss

Tumbled jasper or chert

Microcrystalline quartz (SiO₂), possibly iron-bearing jasper

Jasper with Quartz Vein

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Iron-stained chert or jasper pebble

Microcrystalline quartz (SiO₂), likely hematite/goethite-bearing

Chert with Calcite Veining

Microcrystalline Quartz (SiO2) with Calcium Carbonate (CaCO3) veins

Chert (with Quartz vein)

Chert (Silicon Dioxide, SiO2)

Mixed river pebbles and quartz-rich specimens

Polymictic fluvial gravel; likely quartz, quartzite, chert, and weathered feldspathic rocks

Light-colored granite or granitic gneiss

Granite; typically quartz + feldspar + mica (variable composition)

Rounded gray metamorphic rock, likely quartzite or gneiss

Quartz-rich metamorphic rock; exact identification is uncertain from the photograph

Tumbled gray-green metamorphic rock, likely serpentinite or chlorite schist

Serpentinite/chlorite-rich ultramafic metamorphic rock; commonly dominated by antigorite, lizardite, or chlorite with minor magnetite and talc

Iron-rich chert or jasper fragment

Microcrystalline quartz (SiO₂), commonly hematite/goethite-bearing

Small rounded pebble, likely quartz-rich river stone

Indeterminate; likely quartz/chert-bearing lithic clast

Yellow Quartz

Silicon Dioxide (SiO2)

Limestone

Calcium Carbonate (CaCO3)

Granite with Epidote

Granite, containing quartz, feldspar, and epidote

Polished flint/chert pebble

Microcrystalline quartz (SiO₂), commonly called chert or flint

Chert (with Manganese Oxide coating)

Microcrystalline Quartz (SiO2)

Ironstone Concretion (likely)

Goethite/Hematite/Limonite cemented sediment

Quartz Geode or Druzy Quartz in Host Rock

Silicon Dioxide (SiO2)

Piddock bored rock (likely Mudstone or Shale)

Ichnofossil (Gastrochaenolites borings) in Fine-grained Sedimentary Rock

Mixed rock and mineral collection

Multiple specimens; visible examples may include quartz (SiO₂), amethyst (quartz), calcite (CaCO₃), and dark mafic rocks

Weathered porphyritic volcanic rock

Likely altered andesite or rhyolite porphyry

Yellow Agate

Chalcedony (cryptocrystalline Quartz), SiO2

Unidentified weathered rock fragments

Likely mixed silicate rocks; specific identification requires testing