Mineral (Metamorphic Pseudomorph)

Yellow Aventurine (Yellow Quartzite)

Silicon Dioxide (SiO2) with inclusions

Garnet Schist

Almandine Garnet in Mica Schist (Fe3Al2(SiO4)3)

Epidote

Epidote - {Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)

Rhodonite

Rhodonite (Manganese silicate, (Mn,Fe,Mg,Ca)SiO3)

Rhodonite

Rhodonite (Manganese Iron Magnesium Calcium Silicate) - (Mn,Fe,Mg,Ca)SiO3

Marble

Metamorphic rock composed of Recrystallized Carbonate Minerals (chiefly CaCO3)

Garnet (Almandine/Pyrope series)

Silicate mineral (Almandine: Fe3Al2Si3O12; Pyrope: Mg3Al2Si3O12)

Greenschist (Greenstone River Pebble)

Greenschist (Chlorite Schist)

Quartz Vein in Pelite (Metamorphic Rock)

Hydrothermal Quartz Veining in Metasedimentary Rock (SiO2)

Tumbled Moonstone

Feldspar (Orthoclase/Albite), KAlSi3O8

Gneiss (likely)

Gneiss

Yellow Aventurine

Quartz (Silicon Dioxide - SiO2) with inclusions of Mica

Mica Schist with Quartz

Mica-Quartz Schist (Muscovite subclass)

Prehnite

Prehnite (Ca2Al(AlSi3O10)(OH)2)

Staurolite (Fairy Cross)

Staurolite (Fe2+2Al9Si4O23(OH))

Schist

Schist (various mineralogical compositions including mica, chlorite, talc, etc.)

Dumortierite Quartz

Al7BO3(SiO4)3O3 (Aluminum borate silicate)

Black Sand (Magnetite Sand)

Magnetite (Fe3O4)

Green Quartz (Aventurine)

Silicon Dioxide with Fuchsite inclusions (SiO2 + K(Al,Cr)2(AlSi3O10)(OH)2)

Green Aventurine

Silicon Dioxide (SiO2) with Chromium-rich Fuchsite mica

Mica Schist

Mica Schist (predominantly Muscovite or Biotite sheet silicates)

Pyrite

Iron Sulfide (FeS2)

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.

Mica Schist

Mica Schist (primarily Muscovite or Biotite sheet silicates)

Rhodonite

Rhodonite (MnSiO3)

Epidote (Unakite-related)

Epidote (Ca2(Al,Fe)3(SiO4)3(OH))

Pyrite

Iron Disulfide (FeS2)

Pyrite (Fool's Gold)

Iron Sulfide (FeS2)

Prehnite

Prehnite (Ca2Al(AlSi3O10)(OH)2)

Jadeite and Assorted Corundum (Ruby/Sapphire) / Beryl (Emerald)

Jadeite (NaAlSi2O6), Ruby/Sapphire (Al2O3), Emerald (Be3Al2(SiO3)6)

Greenschist

Greenschist (Actinolite-Chlorite Schist)

Schist

Mica Schist

Biotite Schist

Biotite Schist

Orange Calcite (likely polished specimen)

Calcite

Garnet Schist

Almandine Garnet Schist

Greenschist

Greenschist

Greenschist (Greenstone)

Greenschist (Metamorphic rock containing chlorite, actinolite, and epidote)

Rhodonite in Matrix

Rhodonite (Manganese Silicate) - (Mn2+,Fe2+,Mg,Ca)SiO3

Rhodonite

Rhodonite (Mn, Fe, Mg, Ca)SiO3

Epidote

Epidote Group (Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH))

Epidote (likely Unakite component or Epidosite)

Epidote (Ca2(Al2Fe)(SiO4)(Si2O7)O(OH))

Green Aventurine and Clear Quartz

Aventurine (variety of Quartz - SiO2) and Quartz (SiO2)