Organic Gemstone (Not A Rock Or Mineral In The Traditional Sense, But Bio Mineralized Material)

Sandstone

Arenite (a specific type of sandstone with less than 15% matrix)

Kimberlite

Kimberlite

Mica Schist

Mica Schist (Complex Silicate Rock)

Turquoise

Hydrated phosphate of copper and aluminum (CuAl6(PO4)4(OH)8·4H2O)

Tiger's Eye

Pseudomorph of Crocidolite (SiO2 with iron oxides)

Pink Feldspar

Orthoclase Feldspar (KAlSi3O8)

Sandstone

Arenite (Sedimentary rock composed of sand-sized grains, primarily SiO2)

Sandstone (Micaceous/Feldspathic variant)

Arenite (specifically subarkose or lithic arenite)

Sandstone (with Liesegang rings or Oxidation)

Arenite (primarily Quartz SiO2 with Iron Oxide Fe2O3 staining)

Green Slate (Greenstone)

Foliated Metamorphic Rock (rich in Chlorite/Epidote)

Black Opal

Hydrated Silica (SiO2·nH2O)

Quartz (Milky and Bull Quartz)

Silicon Dioxide (SiO2)

Carnelian Agate

Carnelian (SiO2 with iron oxide impurities)

Fulgurite

Fulgurite (Lechatelierite), amorphous SiO2

Biotite Schist

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

Quartz (Milky or Smoky variant)

Silicon Dioxide (SiO2)

Quartz (Milky or Clear Quartz fragment)

Silicon Dioxide (SiO2)

Sandstone (Ferruginous)

Clastic sedimentary rock (primarily SiO2 with Fe2O3 cement)

Quartz Geode (Citrine or Iron-stained Quartz)

Silicon Dioxide (SiO2)

Tiger's Eye

Pseudomorph of Quartz after Crocidolite (SiO2)

Sandstone (specifically Arkose or Ferruginous Sandstone)

Sandstone (SiO2 with iron oxide inclusions)

Rough Quartz (with potential Host Rock)

Silicon Dioxide (SiO2)

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.

Almandine Garnet

Almandine (Fe3Al2Si3O12)

Sodalite

Sodalite (Na8Al6Si6O24Cl2)

Opal

Hydrated Amorphous Silica (SiO2·nH2O)

Quartz / Rock Crystal

Silicon Dioxide (SiO2)

Agate (specifically Lake Superior Agate style or Banded Chalcedony)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

Clear Quartz (Rock Crystal)

Quartz (Silicon Dioxide, SiO2)

Amethyst

Silicon Dioxide (SiO2) with iron impurities

Gray Agate

Cryptocrystalline Quartz (SiO2)

Carnelian

Carnelian (a variety of Chalcedony, SiO2)

Garnet (Almandine)

Almandine (Fe3Al2(SiO4)3)

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Montana Moss Agate

Chalcedony (Silicon Dioxide, SiO2)

Tiger's Eye

Pseudomorph of Quartz after Crocidolite (SiO2)

Smoky Quartz

Silicon Dioxide (SiO2)

Dyed Agate

Silicon Dioxide (SiO2) with artificial pigment

Turquoise

CuAl6(PO4)4(OH)8·4H2O (Hydrated copper and aluminium phosphate)

Rhodonite

Manganese Silicate (Mn,Fe,Mg,Ca)SiO3

Clear Quartz

Silicon Dioxide (SiO2)

Obsidian

Volcanic glass (high silica volcanic rock)