Sedimentary Or Igneous Fragment

Red Jasper (Opaque Chalcedony)

Silicon Dioxide (SiO2) with Hematite (Fe2O3) inclusions

Chert (Nodule / Geode fragment)

Microcrystalline Quartz (SiO2)

Mammoth Tooth Fragment

Mammuthus primigenius (fossilized dentin and enamel)

Chert (Arrowhead/Tool Grade)

Microcrystalline Quartz (SiO2)

Chalcedony Nodule (Agate/Chert)

Chalcedony (cryptocrystalline Silicon Dioxide, SiO2)

Specular Hematite

Hematite (Fe2O3)

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

Sandstone (Micaceous Sandstone)

Arenite (SiO2 with KAl2(AlSi3O10)(OH)2 inclusions)

Given the appearance, it's likely a fragment of an igneous or metamorphic rock composed of multiple minerals. Without specific diagnostic features, it's difficult to give a common name other than 'crystalline rock fragment'. If pressed to guess based on the granular, somewhat light and dark speckled appearance, it could be a fragment of granite or a related intrusive igneous rock.

As a rock fragment, it does not have a single scientific mineral name; rather, it's a piece of a rock which is a combination of minerals. If it were granite, its main mineral composition would be quartz (SiO2), feldspar (e.g., KAlSi3O8 - orthoclase, (Na,Ca)(Al,Si)4O8 - plagioclase), and mica (e.g., KAl2(AlSi3O10)(OH)2 - muscovite or K(Mg,Fe)3AlSi3O10(OH)2 - biotite), among others.

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Cloudy Quartz / Quartz Tumble

Silicon Dioxide (SiO2)

Chert (variously identified as Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Conglomerate

Conglomerate (SiO2 matrix with various silicate clasts)

Conglomerate

Clastic sedimentary rock (Conglomerate)

Quartz (Druzy)

Silicon Dioxide (SiO2)

White Quartz

Silicon Dioxide (SiO2)

Sandstone (Greywacke)

Arenite / Wacke (Mainly SiO2 with various lithic fragments)

Oolite or Oolitic Limestone

Oolitic Limestone (Principal mineral: Calcite, CaCO3)

Chert (White Chert / Flint)

Microcrystalline or Cryptocrystalline Silicon Dioxide (SiO2)

Quartz (Milky Quartz)

Silicon Dioxide (SiO2)

Granitic Gneiss

Gneiss (containing Potassium Feldspar and Quartz)

Concrete Fragment

Hardened Portland Cement Composite

Chert (specifically a fragment with Desert Varnish)

Microcrystalline quartz (SiO2)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Magnetite

Magnetite (Fe3O4)

Quartz

Silicon Dioxide (SiO2)

Milky Quartz

Silicon Dioxide (SiO2)

Pyrite (Fool's Gold)

Iron Sulfide (FeS2)

Fossilized Wood (with Coal and Limonite)

Petrified Wood (Silicified or Carbonized Flora)

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Quartz (Crystal Fragment)

Silicon Dioxide (SiO2)

Citrine Geode Fragment

Citrine (Silicon Dioxide with Iron Impurities), SiO2

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Quartz (Clear Quartz)

Silicon Dioxide (SiO2)

Granitic Pegmatite (River Rock specimen)

Granite / Pegmatite (composed of SiO2, KAlSi3O8, and NaAlSi3O8)

Granite Sand (Decomposed Granite)

Grus / Quartz-Feldspar Detritus

Chert (Gravel Fragment)

Silicon dioxide (SiO2)

Fossilized Bone Fragment

Permineralized Vertebrate Fossil (Hydroxyapatite replaced by Minerals)

Crinoid Stem Fragment

Crinoid (Phylum Echinodermata, Class Crinoidea)

Coquina with Shell Fragment

Bioclastic Limestone (composed primarily of CaCO3)

Fossilized Bone Fragment

Permineralized Skeletal Element (Likely Vertebrate)