Metamorphic (Pseudo Igneous)

Moonstone

Adularia (Potassium Aluminum Silicate, KAlSi3O8)

Amethyst

Amethyst (variety of Quartz, SiO2)

Quartz Sand Grain

Silicon Dioxide (SiO2)

Smoky Quartz

Smoky Quartz (Silicon Dioxide - SiO2)

Quartz (Milky/Vein Quartz)

Silicon Dioxide (SiO2)

Quartz Pebble (Iron-Stained)

Quartz (Silicon Dioxide - SiO2)

Yellow Quartz (Citrine or Iron-stained Quartz)

Silicon Dioxide (SiO2)

Clear Quartz (Rock Crystal)

Silicon Dioxide (SiO2)

Yellow Quartz (Citrine or Iron-stained Quartz)

Silicon Dioxide (SiO2)

Hypersthene

(Mg,Fe)SiO3 - Enstatite-Ferrosilite series

Ruby (in costume jewelry context)

Corundum (Al2O3) with Chromium impurities

Rough Rose Quartz

Silicon Dioxide (SiO2) with trace amounts of titanium, iron, or manganese

Yellow Quartz (Citrine Quartz Pebble)

Silicon Dioxide (SiO2)

Olivine (often within Peridotite)

Magnesium iron silicate, (Mg,Fe)2SiO4

Clear Quartz Crystal

Silicon Dioxide (SiO2)

Quartz Pebble

Silicon Dioxide (SiO2)

Orange Calcite

Calcium Carbonate (CaCO3)

Granite / Gneiss Complex

Felsic Plutonic Rock (Granite) or High-grade Metamorphic Rock (Gneiss)

Quartz / Vein Quartz

Quartz (Silicon Dioxide, SiO2)

Milky Quartz Mushroom Carving

Quartz (Silicon Dioxide, SiO2)

Smoky Quartz (with possible Feldspar inclusions)

Silicon Dioxide (SiO2)

Blue Sapphire

Corundum (Al2O3)

Pyrite (Fool's Gold)

Iron Disulfide (FeS2)

Garnet (likely Almandine)

Almandine (Fe3Al2(SiO4)3)

Pyrite (on Quartz/Host Rock)

Iron Sulfide (FeS₂)

Gold Ore in Quartz

Auriferous Quartz (Gold: Au; Quartz: SiO2)

Quartz (Milky or Clear Quartz fragment)

Silicon Dioxide (SiO2)

Hematite

Iron(III) oxide (Fe2O3)

Magnetite (potentially as a Lodestone or within Ironstone)

Magnetite (Fe3O4)

Quartz

SiO₂ (Silicon Dioxide)

Clear Quartz (or Rock Crystal)

Quartz (SiO₂ - Silicon Dioxide)

Banded Gneiss

Gneiss (Metamorphic high-grade rock)

Banded Gneiss

Gneiss (Metamorphic high-grade rock)

Gneiss

Gneiss (High-grade regional metamorphic rock)

Gneiss

Gneiss (High-grade metamorphic rock composed primarily of Quartz, Feldspar, and various Micas)

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.

Quartz with Mica (likely Muscovite)

Silicon Dioxide (SiO2) with Potassium Aluminum Silicate Hydroxide Fluoride

Quartz Pebble

Silicon Dioxide (SiO2)

Smoky Quartz

Silicon Dioxide (SiO2)

Pyrite on Quartz

Iron Sulfide (FeS2) on Silicon Dioxide (SiO2)

Quartz (Milky/Cloudy Variety)

Silicon Dioxide (SiO2)

Chrysocolla

Hydrated copper phyllosilicate, Cu2-xAlx(H2-xSi2O5)(OH)4·n(H2O)