Mixed: Igneous And Sedimentary

Rounded gravel / river pebbles

Polymictic alluvial gravel, commonly quartz-, feldspar-, and lithic-rich clasts

Mixed beach gravel and cobbles

Polylithic alluvial or littoral clasts, including quartz, quartzite, chert, limestone, sandstone, and flint

Mixed rounded rock pebbles

Likely granitic gneiss, basaltic rock, and quartz-rich granitic material; exact identification is uncertain from the image

Mixed rock and mineral gravel

Predominantly granite/granodiorite, basaltic rocks, quartz, and possible gneiss; exact identification is uncertain from the image

Rounded, weathered rock (likely quartz-rich granite or gneiss)

Undetermined quartz–feldspar-rich rock; precise identification requires closer examination

Porphyritic granite pebble

Granite, chiefly quartz (SiO₂), alkali feldspar and plagioclase, with minor biotite/hornblende

Granitic Quartz or Pegmatite

Quartz with Orthoclase Feldspar (SiO2 + KAlSi3O8)

Weathered polymictic rock fragment, likely granite-rich conglomerate

Indeterminate mixed lithology; apparent granitic clasts containing quartz, feldspar, and dark mafic minerals

Dalmatian Jasper

Microcrystalline Quartz with Arfvedsonite/Tourmaline inclusions

Granite (Pink/Potassium Feldspar Granite)

Felsic Plutonic Rock (Potassium Feldspar, Quartz, Mica, and Amphibole)

Quartz (Chalcedony/Agate)

Silicon Dioxide (SiO2)

Tumbled Agate

Silicon Dioxide (Chalcedony / Quartz)

Mixed rounded gravel and pebbles

Polymictic clasts, likely including granite, basalt, quartzite, sandstone, and schist

Carnelian Agate (Tumbled)

Chalcedony (SiO2)

Tumbled Agate

Silicon Dioxide (Chalcedony variety), SiO2

Mixed garnet crystal specimens

Garnet-group silicates, likely almandine–spessartine with possible grossular/pyrope varieties; general formula X₃Y₂(SiO₄)₃

Mixed Tumbled Gemstones (Agate, Aventurine, Pyrite, etc.)

Multiple (principally Silicon Dioxide SiO2 and Iron Disulfide FeS2)

Tumbled jasper or chert pebble

Microcrystalline quartz (SiO₂), likely jasper/chert with iron-oxide staining

Crushed limestone gravel

Limestone; predominantly calcite (CaCO₃), possibly dolomitic limestone with dolomite (CaMg(CO₃)₂)

Pyrite-bearing sulfide specimen (likely pyrite)

Pyrite, FeS₂; possibly mixed with pyrrhotite or chalcopyrite

Snowflake Obsidian (possibly mixed with Jasper or other matrix)

Obsidian with Cristobalite inclusions

Mixed landscaping gravel with a pink granite cobble

Primarily granite (quartz, alkali feldspar, plagioclase, biotite); mixed pebble assemblage

Mixed rounded stream pebbles

Most appear to be granitic and mafic igneous rocks, including granite, gneiss, basalt, and possibly quartzite; exact identification is uncertain from the image.

Beach cobbles, predominantly basalt with vesicular volcanic fragments

Basalt (mafic volcanic rock), with possible altered basalt and minor feldspar/quartz-bearing pebbles

Mixed rock fragments, likely basalt and weathered granite

Basalt (mafic volcanic rock) and granitic fragments (quartz–feldspar–mica aggregate)

Concrete

Anthropogenic Sedimentary Rock (Hydrated Calcium Silicate)

Mixed rock and mineral specimens

Multiple unidentified silicate rocks and minerals; likely quartz-bearing material, feldspar, mica, and iron-oxide-bearing stones

Tumbled quartz-rich stone, possibly granite or rhyolite

Likely quartz (SiO₂) with feldspar and minor mica or other inclusions

Crushed granite aggregate

Granite, a coarse-grained felsic intrusive igneous rock composed mainly of quartz, alkali feldspar, plagioclase, and minor mica/amphibole

Tumbled granite or granitic gneiss pebble

Granite/granitic gneiss, chiefly quartz, feldspar, and dark biotite or amphibole

Granite

Granite; primarily quartz, alkali feldspar, plagioclase, and biotite/hornblende

Polished brecciated jasper bracelet

Jasper, microcrystalline quartz (SiO₂), commonly with hematite and iron-oxide inclusions

Weathered granite or granitic gneiss

Granite; chiefly quartz, feldspar, and mica, with iron-oxide weathering

Graphite

Graphite (Native Carbon, C)

Conglomerate (pebble conglomerate)

Clastic sedimentary rock composed of rounded gravel-sized clasts in a finer matrix

Milky quartz (likely quartz-rich rock fragment)

Quartz, silicon dioxide (SiO₂)

Biotite granite (likely weathered granite)

Granite; quartz + feldspar + biotite, with accessory dark minerals

Likely gray granite fragment

Granite, composed mainly of quartz, feldspar, and mica

Weathered polymictic gravel/conglomeratic rock

Polymictic conglomerate or poorly lithified alluvial gravel; chiefly quartz, feldspar, mica, and dark lithic fragments

Mixed rounded gravel and weathered rock fragments

Polymictic alluvial or glacial gravel; composition appears to include basaltic, quartz-rich, and feldspathic clasts

Pink Granite

Phaneritic Plutonic Felsic Rock (K-feldspar rich)

Mixed tumbled quartz specimens

Quartz, silicon dioxide (SiO₂), including rose quartz and milky/included varieties