Sedimentary Rock (Specifically A Concretion Or Possibly A Geode)

Coal (Bituminous or Anthracite)

Carbonaceous sedimentary rock (primarily Carbon, C)

Sandstone (Ferruginous)

Arenite (Fe-bearing Clastic Sedimentary Rock)

Selenite

Gypsum (CaSO4·2H2O), specifically the crystalline variety Selenite

Agate (or Chalcedony)

Silicon Dioxide (SiO2)

Carnelian Agate

Silicon Dioxide (SiO2) with iron oxide impurities

Ironstone (with possible Hematite/Limonite coating)

Ironstone (Fe-rich sedimentary rock)

Mexican Crazy Lace Agate

Silicon Dioxide (SiO2) with iron and aluminum inclusions

Jasper with Quartz Veining

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Milky Quartz Pebble

Quartz (Silicon Dioxide, SiO2)

Coquina Limestone (Fossiliferous Limestone)

Calcareous bioclastic sedimentary rock (CaCO3)

Dragon Stone

Ohko Stone (Argillaceous sedimentary rock)

Conglomerate (Red Sandstone variety)

Clastic Sedimentary Rock (Conglomeratic Sandstone)

Bituminous Coal

Bituminous coal (Organic Sedimentary Rock)

Sandstone (Banded)

Clastic Sedimentary Rock (primarily SiO2)

Ferruginous Sandstone

Clastic Sedimentary Rock (Iron-rich)

Coquina or Fossilized Shell Aggregate

Calcareous bioclastic sedimentary rock (CaCO3)

Sandstone (Quartzose Sandstone)

Clastic Sedimentary Rock (primarily SiO2)

Lignite (Brown Coal)

Humic Lignite (Carbonaceous sedimentary rock)

Sandstone (Ferruginous)

Arenite with Iron Oxides

Quartz

Quartz (Silicon Dioxide, SiO2)

Limonite (Iron Ore)

FeO(OH)·nH2O (Hydrated iron(III) oxide-hydroxide)

Sandstone

Arenite (SiO2 + various cementing minerals)

Limestone Pebble

Calcium Carbonate (CaCO3)

Chert (Septarian or Nodular variety)

Microcrystalline Quartz (SiO2)

Sandstone

Arenite (primarily SiO2)

Chert (Yellow Jasper/Flint)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

Greywacke

Dirty Sandstone (Lithic wacke)

Greyling Sandstone / Greywacke

Lithic Wacke (SiO2 + diverse mineral fragments)

Chert (variations include Flint or Jasper)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Ruby in Zoisite

Ruby (Corundum, Al2O3) in Zoisite (Calcium aluminum silicate hydroxide, Ca2Al3(SiO4)3(OH)) with some Hornblende

Limestone

Calcium Carbonate (CaCO3)

Sandstone

Arenite (primarily SiO2 with various cementing agents)

Gneiss (with Mica and Quartz)

Gneissic Metamorphic Rock

Mica Schist

Mica Schist (primarily Muscovite and Biotite composition)

Biotite Schist

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

Sandstone (Quartz-rich)

Arenite (SiO2 based)

Sandstone (Ferruginous)

Arenite (variable SiO2 with Fe2O3 staining)

Chert (and/or Flint)

Silicon dioxide (SiO2)

Sandstone (likely Arkosic or Lithic)

Clastic Sedimentary Rock (SiO2 with accessory minerals)

Sandstone (Quartzose)

Arenite (primarily SiO2)

Gneiss (Metamorphic Rock)

Gneiss (variable mineral formula primarily containing Quartz, Feldspar, and Mica)

River Stone (likely Siltstone or fine-grained Sandstone)

Clastic Sedimentary Rock (Lithic Wacke / Siltstone)