Mineral With Metamorphic Or Sedimentary Host

Jasper Conglomerate (Puddingstone)

Siliceous Conglomerate (Quartz and Jasper clasts in a fine-grained matrix)

Fluorite and Rose Quartz

Fluorite (CaF2), Rose Quartz (SiO2)

Quartz

Silicon Dioxide (SiO2)

Gneiss (Gneissic Granite)

Gneiss

Quartzite with Iron Banding

Metamorphosed Quartz-rich Sandstone (SiO2 with Fe2O3 inclusions)

Anthracite Coal

Anthracite (Carbon Content: 86%-97%)

Garnet Schist

Garnetiferous Micaceous Schist

Greenstone / Chert

Cryptocrystalline Quartz (SiO2) or Altered Basalt

Amethyst

Quartz (SiO2) with trace iron impurities

Agate (specifically, likely a geode slice or nodule)

Agate (a variety of Chalcedony, with chemical formula SiO2)

Quartz (likely Clear Quartz or Rock Crystal)

Quartz (SiO2)

Green Aventurine

Aventurine Quartz (SiO2 + Fuchsite inclusions)

Anthracite Coal

Anthracite (Carbon-based organic sedimentary/metamorphic rock)

Coal (Anthracite)

Anthracite (Carbon-based organic sedimentary/metamorphic rock)

Gold Ore (in Quartz/Pyrite)

Native Gold (Au) with Quartz (SiO2) and Pyrite (FeS2)

Prehnite

Prehnite (Ca2Al(AlSi3O10)(OH)2)

Spessartine Garnet in Quartz/Feldspar Pegmatite

Spessartine (Mn3Al2(SiO4)3) in Quartz (SiO2) and Feldspar

Black Sand (Magnetite Sand)

Magnetite (Fe3O4)

Yellow Quartzite (River Stone)

Quartzite (primarily SiO2)

Quartz

Quartz (SiO₂ - Silicon Dioxide)

Slate

Slate (a fine-grained, foliated metamorphic rock). Mineral composition: Primarily composed of mica minerals (muscovite, chlorite, sericite) and quartz, with minor amounts of hematite, pyrite, and other accessory minerals.

Quartzite (Banded)

Metamorphosed Sandstone (SiO2 with impurities)

Yellow Jasper

Silicon Dioxide (SiO2) with iron oxide inclusions

Red Jasper

Silicon Dioxide (SiO2) with Hematite inclusions

Tiger's Eye

Pseudomorph of Quartz after Crocidolite (SiO2)

Quartzite

Quartzite (primarily SiO2)

Feldspar-rich Quartzite

Meta-arkose (Quartz-Feldspar Quartzite)

Quartzite Pebble (River Rock)

Quartzite (mainly SiO2)

Greenschist (Greenstone River Pebble)

Greenschist (Chlorite Schist)

Orthoclase Feldspar with Quartz

Orthoclase (KAlSi3O8)

Quartzite with Chert inclusions

Metamorphosed Quartz-rich Rock (SiO2)

Yellow Aventurine

Quartz (Silicon Dioxide - SiO2) with inclusions of Mica

Epidote

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

Quartz with Muscovite Mica

Silicon Dioxide (SiO2) with Potassium Aluminum Silicate Hydroxide Fluoride (KAl2(AlSi3O10)(F,OH)2)

Biotite Schist

Biotite-rich Schist

Marble

Metamorphic rock composed of Recrystallized Carbonate Minerals (chiefly CaCO3)

Quartzite

Quartzite (SiO2 silicon dioxide)

Mica Schist

Mica Schist (primarily Muscovite or Biotite KAl2(AlSi3O10)(OH)2)

Quartzite

Metamorphosed Quartz Sandstone (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.

Rhodonite

Rhodonite (MnSiO3)

Pietersite

Brecciated Crocidolite in Quartz (Chalcedony)