Multiple

Peridot (Olivine)

Magnesium Iron Silicate (Mg, Fe)2SiO4

Agate

Chalcedony (cryptocrystalline variety of Quartz, SiO2)

Agate Geode / Nodular Chalcedony

Silicon Dioxide (SiO2) with impurities

Peridot

Olivine (Magnesium Iron Silicate - (Mg, Fe)2SiO4)

Unakite

Altered Granite (Epidotized Granite)

Gneiss

Felsic banded gneiss, chiefly quartz–feldspar–mica

Fancy Jasper

Chalcedony (SiO2)

Quartz Vein in Host Rock (likely Sandstone or Mudstone)

Silicon Dioxide (SiO2) within Sedimentary Matrix

Quartz Vein in Rhyolite

Silicon Dioxide (SiO2) in extrusive igneous rock

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.

Lapis Lazuli

Lapis Lazuli (A complex rock primarily composed of Lazurite: (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)

Lapis Lazuli

Lapis Lazuli (Mineral composition: Lazurite (Na,Ca)8(AlSiO4)6(SO4,S,Cl,OH)2, Calcite, and Pyrite)

Trilobite Fossil

Trilobita (Class), likely Phacopid or Asaphid order

Quartz Vein / Milky Quartz

Silicon Dioxide (SiO2)

Botryoidal Chalcedony Geode

Silicon Dioxide (SiO2) - Chalcedony / Cryptocrystalline Quartz

Botryoidal Chalcedony (Agate/Chert Nodule)

Chalcedony (SiO2)

Botryoidal Chalcedony in Geode/Vug

Silicon Dioxide (SiO2)

Lunar Feldspathic Breccia

Lunar Meteorite (Feldspathic Regolith Breccia)

Sphalerite with Galena

Zinc Sulfide ((Zn,Fe)S) and Lead Sulfide (PbS)

Fossilized Brachiopod

Brachiopoda (Phylum), likely Order Spiriferida or Rhynchonellida

Quartzite Pebble

Quartzite (SiO2)

Lapis Lazuli (Low-grade)

Lapis Lazuli (Aggregate of Lazurite, Calcite, and Pyrite)

Jasper with Quartz Veining

Silicon Dioxide (SiO2)

Lapis Lazuli

Lapis Lazuli (Primary mineral: Lazurite, (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)

Lapis Lazuli

Lapis Lazuli (Complex aggregate mainly of Lazurite: (Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)

Lapis Lazuli

Na8[Al6Si6O24]S2 (Lazurite component), a rock composed primarily of Lazurite, Calcite, and Pyrite

Quartzite with Chlorite Bands

Meta-quartzite with Chlorite (Mg,Fe,Li)6AlSi3O10(OH)8

Rainbow Moonstone

White Labradorite (formula: (Na,Ca)(Al,Si)4O8)

Lapis Lazuli

Lazurite-rich metamorphic rock ((Na,Ca)8(AlSiO4)6(S,Cl,SO4,OH)2)

Bivalve Fossil (Internal Mold/Steinkern)

Class Bivalvia (Fossilized Mold)

Gneiss boulder

Banded granitoid gneiss; chiefly quartz, feldspar, and biotite/hornblende

Quartz Pebble

Silicon Dioxide (SiO2)

Quartzite Cobble

Quartzite (SiO2)

Lapis Lazuli

Lazurite-rich metamorphic rock

Fancy Jasper

Jasper (Cryptocrystalline Quartz, SiO2)

Lapis Lazuli

Na8(Al6Si6O24)S2 (Lazurite is the primary constituent mineral)

Orthoceras fossil

Orthoceras regulare (Cephalopoda, Orthocerida)

Ironstone / Hematite

Iron(III) oxide (Fe2O3)

Fancy Jasper (Agate/Chert mix)

Silicon Dioxide (SiO2) with various inclusions

Quartzite Cobble

Quartzite (SiO2)

Diamond (Cluster Setting)

Carbon (C) - Diamond

Unakite

Epidotized Granite