Igneous Or Metamorphic (Base Stone); Anthropogenic (Decoration)

Citrine Quartz

Silicon Dioxide (SiO2)

Sandstone (Arkose)

Arkose Sandstone (principally SiO2 with Feldspar)

Iron-rich vesicular rock, possibly slag or weathered basalt

Identification uncertain; likely ferruginous basalt/ironstone, with possible anthropogenic iron slag

Quartzite

Metamorphic Quartzite (SiO2)

Biotite on Quartz Matrix

Biotite - K(Mg,Fe)3(AlSi3O10)(OH,F)2 with Quartz (SiO2)

Mica-rich Pegmatite

Pegmatite (rich in Muscovite and Biotite)

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.

Granite Pebble

Granite (Felsic Intrusive Igneous Rock)

Epidote

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

River Stone (Basalt Porphyry)

Porphyritic Basalt

Chert (Arrowhead Fragment)

Microcrystalline Quartz (SiO2)

Mica (Muscovite) in Granite

Muscovite (KAl2(AlSi3O10)(OH)2)

Granite

Granite (Felsic Plutonic Rock)

Milky Quartz

Silicon Dioxide (SiO2)

Epidote-bearing Rock / Epidote Inclusion

Epidote (Ca2(Al, Fe)3(SiO4)3(OH)) in host rock

Milky Quartz

Silicon Dioxide (SiO2)

Fuchsite Schist with Quartz

Chromian Muscovite [K(Al,Cr)2(AlSi3O10)(OH)2] Schist

Vesicular Basalt (Lava Rock)

Basalt

Basalt

Extrusive igneous rock

Banded Agate Geode (with Microcrystalline Quartz)

Silicon Dioxide (SiO2) - variety Chalcedony/Agate

Biotite Schist

Biotite Schist (K(Mg,Fe)3AlSi3O10(OH,F)2)

Schist

Mica Schist (formula variable based on mineral content, typically containing [K,Al,Fe,Mg,Si,O,H])

Black Tourmaline (Schorl)

Schorl (Sodium iron silicate hydroxide boron silicate); NaFe3Al6(BO3)3Si6O18(OH)4

Green Slag Glass

Amorphous Silicon Dioxide (with metallic impurities)

Muscovite Mica

Muscovite (KAl2(AlSi3O10)(OH)2)

Muscovite Mica

Muscovite - KAl2(AlSi3O10)(OH)2

Muscovite

KAl2(AlSi3O10)(OH)2

Quartzite Pebble

Quartzite (SiO2)

Quartz with Mica / Chlorite Inclusion

Silicon Dioxide (SiO2) with Phyllosilicate minerals

Map Jasper (Picasso Stone)

Metamorphosed Calcium Carbonate (Crystalline Limestone or Marble with Silicate inclusions/impurities)

Aventurine

Aventurine Quartz (SiO2 with inclusions)

Quartz with Mica (Gneissic or Pegmatitic origin)

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

Rough Agate/Chert Nodules

Cryptocrystalline Quartz (SiO2)

Mixed polished river pebbles, predominantly quartzite and quartz

Quartzite (SiO₂), quartz (SiO₂), with possible feldspar-rich and iron-stained lithologies

Basalt with Vesicular Amygdule

Extrusive igneous rock (Mafic)

Aventurine

Quartzite (SiO2 with inclusions)

Muscovite Mica

Muscovite (KAl2(AlSi3O10)(OH)2)

Mica Schist

Mica Schist (primarily Muscovite or Biotite)

Quartzite Pebble

Metamorphosed Quartz Sandstone (SiO2)

Diorite

Intermediate Phaneritic Igneous Rock

Obsidian Arrowhead

Volcanic Glass (Primary composition: SiO2)

Quartzite River Cobble

Quartzite (primarily SiO2)