Metamorphic

Rhodonite

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

Muscovite Mica

Muscovite: KAl2(AlSi3O10)(OH)2

Zoisite with Ruby

Anyolite (Ca2Al3(SiO4)3(OH) with Al2O3:Cr)

Nephrite Jade

Ca2(Mg, Fe)5Si8O22(OH)2

Seraphinite

Clinochlore (a variety of the chlorite group)

Tiger's Eye

Pseudomorph of quartz after crocidolite (SiO2 with iron oxide inclusions)

Quartzite with Chlorite

Metamosphosed Quartz Sandstone (SiO2 with (Mg,Fe)3(Si,Al)4O10(OH)2 inclusions)

Schist

Mica Schist

Schist

Schist (various mineral compositions)

Blue Sapphire

Corundum (Al2O3)

Unakite (Epidotized Granite)

Unakite; primarily composed of Epidote (Ca2(Al,Fe)3(SiO4)3(OH)), Orthoclase (KAlSi3O8), and Quartz (SiO2)

Schist

Mica Schist (predominantly Muscovite or Biotite)

Anthracite Coal

Anthracite (Carbon-rich metamorphic coal)

Greenschist / Migmatite

Regional Metamorphic Complex (Facies: Greenschist to Amphibolite)

Nephrite Jade

Nephrite (a variety of the mineral actinolite within the amphibole group); Chemical Formula: Ca2(Mg,Fe)5Si8O22(OH)2

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.

Quartzite (River-worn Shiner)

Quartzite (Formula: SiO2)

Banded Gneiss

Gneiss (High-grade metamorphic rock typically composed of Quartz, Feldspar, and Mica)

Schist/Phyllite

Metamorphic Schist (Chlorite Schist variety)

Cream Marble (Speckled)

Metamorphosed Limestone (mainly CaCO3)

Greenschist

Chlorite schist

White Quartz (Milky Quartz)

Quartz (Silicon Dioxide - SiO2)

Biotite (Black Mica)

Biotite - K(Mg,Fe)3(AlSi3O10)(OH)2

Greenschist / Chloritaform Schist

Chlorite Schist (Group of Silicate Minerals)

Quartzite

Quartzite (primarily SiO2)

Quartzite pebble

Quartzite (SiO2)

Epidote in Matrix (Unakite-related)

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

Milky Quartz with Iron Staining

Silicon Dioxide (SiO2)

Quartz Vein in Host Rock

Quartz (SiO2) in Mafic or Sedimentary Matrix

Yellow Quartz (Citrine/Yellow Jasper mix)

Silicon Dioxide (SiO2)

River Quartzite (or Quartz Cobble)

Quartzite (primarily Silicon Dioxide - SiO2)

Fuchsite Gneiss (Green Quartzite)

Chromium-rich Muscovite (KAl2(AlSi3O10)(OH)2 with Cr replacements)

Schist (Micaceous Schist)

Schist (containing mainly Muscovite and Quartz)

Marble

Metamorphic rock composed of Recrystallized Carbonate Minerals (chiefly CaCO3)

Milky Quartz

Silicon Dioxide (SiO2)

Pink Quartz (Rose Quartz variant)

Silicon Dioxide (SiO2)

Quartzite Cobble

Quartzite (primarily SiO2)

Milky Quartz

Silicon Dioxide (SiO2)

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Quartzite

Quartzite (SiO2)

Gossan (Iron Hat)

Limonitic Gossan (Fe-oxide/hydroxide complex)

Quartzite

Quartzite (SiO2)