Mineral (Man Enhanced)

Banded Agate (specifically Moss Agate or Plume Agate variety)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

Rose Quartz

Silicon Dioxide (SiO2)

Moss Agate / Carnelian Agate

Silicon Dioxide (SiO2) with iron and manganese inclusions

Diamond

Carbon (C), specifically a solid form of the element carbon with atoms arranged in a crystal structure called diamond cubic.

Diamond

Diamond (C)

Amber

Succinite (fossilized tree resin)

Sandstone Geode (Ironstone Concretion)

Arenite with Limonite/Hematite matrix (SiO2 with Fe-oxides)

Granite

Phaneritic Felsic Igneous Rock

Yellow Quartzite River Cobble

Meta-quartzite (SiO2 with iron oxide staining)

Amber

Succinate (Fossilized Tree Resin)

Basaltic Tuff / Volcanic Breccia

Pyroclastic Breccia / Lithic Tuff

Serpentine (Serpentinite)

Serpentinite (complex silicate group including lizardite, chrysotile, and antigorite)

Chert (Iron-stained)

Microcrystalline Quartz (SiO2)

Granite Cobble

Felsic Intrusive Igneous Rock (composed of Quartz, Alkali Feldspar, and Plagioclase)

Granite

Phaneritic Igneous Rock (primarily Quartz, Feldspar, and Mica)

Amber

Succinite (Fossilized Tree Resin)

Pearl (Imitation or Cultured)

Calcium Carbonate (Aragonite/Calcite) - CaCO3

Chert (Chert / Flint nodule)

Silicon Dioxide (SiO2)

Chert (Grey Chert)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Quartzite (Milky Quartz Cobble)

Silicon Dioxide (SiO2)

Chert (specifically Banded Chert)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Sandstone (Ferruginous)

Clastic sedimentary rock (primarily SiO2 with Fe2O3 cement)

Sandstone (Ferruginous)

Arenite (Fe-rich)

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.

Serpentinite

Serpentinite (composed primarily of Serpentine minerals: Mg3Si2O5(OH)4)

Sandstone

Arenite (composed primarily of SiO2)

Sandstone (Ferruginous)

Arenite (primarily SiO2 with Iron Oxide cement)

Sandstone (with Liesegang rings or Oxidation)

Arenite (primarily Quartz SiO2 with Iron Oxide Fe2O3 staining)

Sandstone (Quartzose)

Arenite (primarily SiO2)

Banded Sandstone

Arenite (composed primarily of Quartz: SiO2)

Amethyst Sage Agate

Silicon Dioxide (SiO2) with trace minerals (Manganese/Iron oxides)

Sandstone

Sandstone (lithified quartz arenite, arkose, graywacke, etc. depending on composition)

Petrified Wood

Silicified Wood (SiO2)

Sandstone (Quartz-rich Pebble)

Arenite (primarily SiO2)

Sandstone (with Iron Staining)

Arenite (composed primarily of SiO2 with Fe2O3 staining)

Chert (Nodular Chert)

Microcrystalline Silica (SiO2)

Moss Agate

Silicon Dioxide (SiO2) with inclusions of manganese or iron oxides

Granite Pebble (Salt and Pepper Granite)

Felsic Intrusive Igneous Rock (Granite)

Petrified Wood

Silicified Wood (SiO2)

Rose Quartz

Quartz (SiO₂), specifically a variety of Quartz

Milky Quartz with Mineral Inclusions

Quartz (Silicon Dioxide, SiO2)

Serpentinite

Serpentinite (composed primarily of Serpentine group minerals: (Mg,Fe)3Si2O5(OH)4)