Metamorphic (Modified)

Quartz with Schist Inclusion

Crystalline Silicon Dioxide (SiO2) with Muscovite/Biotite Schist

Mica Schist

Muscovite-Biotite Schist

Milky Quartz

Silicon Dioxide (SiO2)

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Serpentine

Antigorite, Lizardite, and Chrysotile (Mg3Si2O5(OH)4)

Milky Quartz

Silicon Dioxide (SiO2)

Quartz with Mica inclusions (likely Schist or Gneiss host)

Silicon Dioxide (SiO2) with Phyllosilicates (KAl2(AlSi3O10)(OH)2)

Schist

Mica Schist

Yellow Quartz (Citrine/Yellow Chalcedony)

Silicon Dioxide (SiO2)

Schist

Mica Schist

Muscovite Schist

Muscovite (KAl2(AlSi3O10)(OH)2) in Schist

Mica Schist with Garnet

Garnetiferous Mica Schist

White Quartz (Milky Quartz)

Silicon Dioxide (SiO2)

Milky Quartz

Silicon Dioxide (SiO2)

Garnet Schist

Almandine Garnet Schist

Milky Quartz

Silicon Dioxide (SiO2)

Red Quartzite Slipper Stone

Quartzite (SiO2)

Smoky Quartz (with inclusions)

Silicon Dioxide (SiO2)

Schist

Mica Schist

Schist

Mica Schist

Milky Quartz

Quartz / Silicon Dioxide (SiO2)

Quartzite

Quartzite (SiO2)

Nephrite Jade

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

Pink Quartz (Inclusion-rich Quartzite)

SiO2 (Silicon Dioxide) with Iron Oxide / Hematite inclusions

Pink Gneiss / Pink Granite Gneiss

Felsic Gneiss (dominated by Orthoclase Feldspar and Quartz)

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

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.

Schist

Mica Schist

Epidote

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

Schist

Schist (various mineral compositions)

Gneiss (likely)

Gneiss

Quartzite (River-worn Shiner)

Quartzite (Formula: SiO2)

Banded Gneiss

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

Greenschist

Chlorite schist

Epidote

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

Magnetite

Magnetite (Iron(II,III) oxide, Fe3O4)

Quartzite Pebble

SiO2 (Silicon Dioxide)

Unakite

Epidotized Granite

Chlorite (Small Flakes/Sand)

Chlorite Group (Magnesium Iron Aluminum Silicate Hydroxide - (Mg,Fe)3(Si,Al)4O10(OH)2·(Mg,Fe)3(OH)6)

Rhodonite

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