Mineral, Specifically A Rock Fragment

Pink Granite

Granite (Alkali-feldspar granite)

Milky Quartz

Silicon Dioxide (SiO2)

Moss Agate

Silicon Dioxide with inclusions (SiO2 + Fe/Mn/Mg)

Breccia

Breccia - Clastic sedimentary rock

Breciated Jasper

Silicon Dioxide (SiO2) with iron oxide inclusions

Milky Quartz

Quartz (Silicon Dioxide - SiO2)

Sandstone

Arenite (primarily SiO2)

Granite

Plutonic felsic igneous rock

Sandstone (with potentially high Feldspar/Arkose content)

Clastic sedimentary rock (SiO2 dominated)

Chalcedony (Botryoidal Agate vein)

Chalcedony (Microcrystalline Quartz) - SiO2

Fire Opal (in Matrix)

Hydrated Silica (SiO2·nH2O)

Dendritic Agate (specifically Orange/Tumbled)

Silicon Dioxide (SiO2) with Oxide Inclusions

Dalmatian Stone (Dalmation Jasper)

Aplite with Arfvedsonite inclusions

Dalmation Stone (often called Dalmatian Jasper)

Antiperthite-rich Microgranite

Green Aventurine

Aventurine Quartz (SiO2 with inclusions)

Banded Agate

Chalcedony / Silicon Dioxide (SiO2)

Concretion or Geode (unbroken)

Varied (depending on mineral composition and cementing agent). For quartz-lined geodes, the scientific name of the dominant mineral would be Quartz (SiO2). For calcite-lined geodes, Calcite (CaCO3). Concretions are often composed of cryptocrystalline quartz (chert), calcite, or iron oxides.

Sandstone

Arenite (SiO2 primarily)

Thunderegg (specifically a Jasper/Agate-filled Geode nodule)

Silicon Dioxide (SiO2) within Rhyolitic Matrix

Basalt with Epidote Veins

Mafic Igneous Rock (Basalt)

Smoky Quartz

Silicon Dioxide (SiO2)

Sandstone

Clastic sedimentary rock (primarily SiO2)

Ocean Jasper

Spherulitic Chalcedony (SiO2)

Marble

Recrystallized Calcite (CaCO3) or Dolomite (CaMg(CO3)2)

Hag Stone

Perforated Sedimentary Rock (typically Limestone or Sandstone)

Agate (Fortification Agate)

Banded Chalcedony (SiO2)

Ethiopian Fire Opal

Hydrated Silica (SiO2·nH2O)

Flower Agate (Plume Agate)

Chalcedony (Silicon Dioxide) with Spherulitic Inclusions - SiO2

Brecciated Jasper

Silicon Dioxide (SiO2) with Hematite impurities

Agate

Silicon Dioxide (SiO2)

Sardonyx Cameo

Silicon Dioxide (SiO2) - variety Cryptocrystalline Quartz

Clear Quartz (Druzy)

Crystalline Silicon Dioxide (SiO2)

Orange Quartzite / Carnelian Agate

Silicon Dioxide (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.

Conglomerate

Clastic sedimentary rock (Conglomerate)

Quartz / Quartzite Fragment

Silicon Dioxide (SiO2)

Muscovite Mica

Muscovite / KAl2(AlSi3O10)(OH)2

Milky Quartz

Quartz (Silica / Silicon Dioxide), SiO2

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Vesicular Basalt (Scoria)

Extrusive Mafic Igneous Rock (primarily Plagioclase Feldspar and Pyroxene)

Smoky Quartz

Smoky Quartz (Silicon Dioxide - SiO2)

Pink Granite

Phaneritic Felsic Igneous Rock