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

Amethyst

Silicon Dioxide with trace Iron (SiO2)

Milky Quartz

Silicon Dioxide (SiO2)

Basalt

Extrusive Igneous Rock

Green Aventurine

Silicon Dioxide (SiO2) with Fuchsite inclusions

Black Marble

Recrystallized Limestone (CaCO3)

Granite Pebble

Granite (Felsic Intrusive Igneous Rock)

Mica-rich Schist fragment

Mica Schist

Schist

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

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.

Basalt River Stone

Aphanitic Mafic Volcanic Rock

Dark mafic rock, likely basalt

Basalt; chiefly plagioclase feldspar and pyroxene, with possible olivine and iron oxides

Biotite (Black Mica)

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

Granite

Phaneritic Felsic Igneous Rock

Chlorite (Small Flakes/Sand)

Chlorite Group (Magnesium Iron Aluminum Silicate Hydroxide - (Mg,Fe)3(Si,Al)4O10(OH)2·(Mg,Fe)3(OH)6)

Green Aventurine

Quartz variety (SiO2 with inclusions)

Mica-rich Pegmatite

Pegmatite (rich in Muscovite and Biotite)

Milky Quartz

Silicon Dioxide (SiO2)

Muscovite Mica

Muscovite (Potassium Mica) KAl2(AlSi3O10)(OH)2

Epidote

Epidote (Ca2(Al,Fe)3(SiO4)3(OH))

Fuchsite Schist with Quartz

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

Amethyst

Silicon Dioxide (SiO2) with Fe3+ impurities

Granite

Granite (Felsic Plutonic Rock)

Raw Emerald in Matrix

Beryl (Be3Al2Si6O18) with Chromium/Vanadium impurities

Quartz with Mica / Chlorite Inclusion

Silicon Dioxide (SiO2) with Phyllosilicate minerals

Muscovite Mica

Muscovite (KAl2(AlSi3O10)(OH)2)

Quartz / Quartz Cluster

Silicon Dioxide (SiO2)

Epidote with Quartz

Ca2(Al,Fe)3(SiO4)3(OH) (Epidote) / SiO2 (Quartz)

Quartz with Mica (Gneissic or Pegmatitic origin)

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

Chert (Arrowhead)

Microcrystalline Quartz (SiO2)

Polished river pebble

Indeterminate fine-grained fluvial clast, likely sandstone or chert

Map Jasper (Picasso Stone)

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

Granite Cobble / Gneiss (River Rock)

Granitic Gneiss / Felsic Igneous Rock

Muscovite Mica

Muscovite (KAl2(AlSi3O10)(OH)2)

Epidote

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

Basalt River Cobble

Basalt (Aphanitic extrusive mafic igneous rock)

Blue gemstone in a decorative setting (possibly blue spinel or sapphire)

Unidentified blue faceted gemstone; sapphire is corundum (Al₂O₃), while spinel is MgAl₂O₄

Granite Pebble

Granite (Plutonic Igneous Rock)

Muscovite Mica

Muscovite (KAl2(AlSi3O10)(OH)2)

Likely biotite mica

Biotite, a dark mica-group mineral; approximate formula K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂

Quartz with Muscovite Mica

SiO2 with KAl2(AlSi3O10)(OH)2

Granite / Quartz Vein Rock

Granitoid with Quartz (SiO2)

Mica Schist

Mica Schist (primarily Muscovite or Biotite)