Sedimentary Or Igneous

Pyrite

Iron Sulfide (FeS2)

Likely serpentinite (serpentine-rich rock)

Serpentinite, composed mainly of serpentine-group minerals (e.g., antigorite, lizardite, or chrysotile)

Iron-stained milky quartz

Quartz (SiO₂), with iron-oxide staining

Pebble (likely a type of sandstone or quartzite pebble)

Clastic Sediment (specifically, a rudite-sized clast). If the pebble is composed of a specific rock type, its scientific name would be that rock type (e.g., 'Quartzite pebble', 'Granite pebble', 'Chert pebble'). Given its appearance, it is likely a metamorphic quartzite pebble or a hard sandstone pebble.

Quartz Geode

Silicon Dioxide (SiO2) within Sedimentary or Igneous host

Quartz Vein in Host Rock

Silicon Dioxide (SiO2) within Sedimentary or Igneous Matrix

Quartz Geode

Silicon Dioxide (SiO2) within a sedimentary or igneous host

Iron-stained quartz-rich rock (possibly ironstone or ochre-coated quartz)

Undetermined ferruginous rock; yellow-brown coloration likely from goethite and/or limonite (hydrated iron oxides)

Geode (Unopened)

Quartz/Chalcedony concretion

Garnet

Garnet (X3Y2(SiO4)3)

Agate Geode

Silicon Dioxide (SiO2) - Chalcedony variety

Garnet Gneiss

Garnetiferous quartzo-feldspathic gneiss

Small rounded pebble, likely quartz-rich sandstone or granitoid fragment

Uncertain; probable quartz/feldspar-bearing lithic pebble

Small weathered mineral/rock fragment

Uncertain from image; possibly quartz-rich sandstone or a feldspar-bearing rock

Geode

Quartz / Chalcedony nodule

Gneissic Schist

Gneiss-schist (Metamorphic rock)

Rounded river pebble, likely quartz-rich sandstone or weathered igneous rock

Indeterminate; possibly quartzite, sandstone, or fine-grained granitic rock

Mica-rich schist (probable)

Foliated quartz–mica schist; likely containing quartz, muscovite and/or biotite

Garnet Gneiss

Gneiss containing Almandine Garnet

Likely mica-rich schist (possibly phyllite)

Muscovite–biotite schist; exact identification requires examination of a fresh surface

Geode

Quartz / Chalcedony nodule

Quartz Geode / Druzy Quartz Node

Silicon Dioxide (SiO2)

Garnet in Host Rock

Garnet Group (A3B2(SiO4)3)

Foliated metamorphic cobble, likely gneiss

Biotite–quartz–feldspar gneiss (tentative)

Gneiss

Gneiss (Metamorphic Rock)

Fluorite Bracelet

Calcium Fluoride (CaF2)

Quartz Geode

Silicon Dioxide (SiO2)

Mica-rich schist

Mica schist, likely muscovite–biotite schist with quartz

Mica-rich metamorphic rock, likely biotite schist

Biotite–quartz schist; probable composition of quartz, biotite, feldspar, and minor sulfide or iron-oxide minerals

Opal

Hydrated Silica (SiO2·nH2O)

Small rounded pebble, likely quartz-rich sandstone or granitic fragment

Indeterminate lithic clast; possible quartz–feldspar aggregate

Geode

Quartz nodule / Chalcedony-lined cavity

Mica-rich rock, likely mica schist

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

Mica schist (likely biotite–muscovite schist)

Mica schist; chiefly quartz and mica minerals (muscovite KAl₂(AlSi₃O₁₀)(OH)₂ and/or biotite)

Weathered foliated metamorphic rock, likely schist or gneiss

Micaceous schist/gneiss; composition likely quartz, feldspar, mica, and altered mafic minerals

Weathered schist or gneiss fragment

Quartz–feldspar–mica metamorphic rock; likely mica schist or gneiss

Gneiss (with Garnet)

Gneiss (Feldspar-Quartz-Biotite-Garnet Metamorphic Rock)

Fluorite with Quartz coating

Calcium Fluoride (CaF2) with Silicon Dioxide (SiO2)

Likely mica schist

Mica-rich schist, probably muscovite–biotite schist

Weathered quartz-rich metamorphic rock, likely gneiss or quartzite

Quartz–feldspar–mica metamorphic rock; exact identification is uncertain from the photograph

Fluorite

Calcium Fluoride (CaF2)

Geode with Quartz Crystals

SiO2 (Silicon Dioxide) in a geode formation