Mineral (Processed Alloy)

Banded Sandstone / Quartzite Pebble

Sedimentary quartz arenite with liesegang banding

Unidentified metallic mineral fragment

Indeterminate; possibly galena, hematite, or a metallic meteorite fragment

Dalmatian Jasper

Feldspar porphyry (Microcline and Quartz with Arfvedsonite spots)

Hematite

Iron Oxide (Fe2O3)

Blue Quartz

Silicon Dioxide (SiO2) with inclusions

Taaffeite

BeMgAl4O8 (Beryllium Magnesium Aluminum Oxide)

Green Calcite

Calcium Carbonate (CaCO3)

Assorted Tumbled Gemstones

Mixed oxides and silicates (including Quartz, Chalcedony, and Feldspar variants)

Dyed Quartz (often sold as 'Blue Quartz' or 'Blue Agate')

Silicon Dioxide (SiO2) with artificial pigment

Prehnite

Prehnite (Ca2Al(AlSi3O10)(OH)2)

Petrified Wood

Silicified Wood (SiO2)

Yellow Aventurine (Yellow Quartzite)

Silicon Dioxide (SiO2) with inclusions

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

Chalcopyrite in Quartz (Gossan/Iron Hat)

CuFeS2 (Chalcopyrite) with SiO2 (Quartz)

Quartz Pebble

Silicon Dioxide (SiO2)

Tiger's Eye

Silicon Dioxide (SiO2) with fibrous inclusions

Smoky Quartz

SiO2 (Silicon Dioxide)

Quartz Vein in Matrix

Silicon Dioxide (SiO2) within Rhyolitic or Granitic Matrix

Likely polished quartz or glass-like mineral cabochon

Probably quartz (SiO₂), though the image cannot exclude man-made glass

Yellow Quartz Pebble

SiO2 (Silicon Dioxide) with Iron Impurities

Nugget of Native Silver

Native Silver (Ag)

Bismuth

Bismuth (Bi)

Rose Quartz

Silicon Dioxide (SiO2)

Likely tumbled yellow-orange mineral or glassy stone

Indeterminate from photograph; possibilities include yellow jasper, calcite, agate, or dyed quartz

Unidentified dark rock fragment

Likely fine-grained mafic mineral aggregate; exact identification requires testing

Sandstone

Arenite (SiO2 primarily)

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

Eagle Eye / Grey Tiger Eye

Pseudomorph of Quartz after Crocidolite (SiO2)

Sulfur on Aragonite

Sulfur (S) on Aragonite (CaCO3)

Petrified Wood

Silicified Wood (SiO2)

Banded Gneiss

Banded Gneiss (High-grade Metamorphic 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.

Greenstone with Epidote or Quartz veins

Metabasalt (Greenstone facies)

Fossil Shark Tooth

Selachii fossil

Pyrite in Matrix

Iron Sulfide (FeS2)

Aragonite Star Cluster

Aragonite (Calcium Carbonate, CaCO3)

Quartz (Common or Milky Quartz)

Silicon Dioxide (SiO2)

Coprolite

Fossilized Feces

Petrified Wood

Silicified Wood (SiO2)

Quartz with Mafic Inclusions

Silicon Dioxide (SiO2) with host igneous matrix

Limonite Stained Basalt

Hydrated Iron Oxide on Mafic Volcanic Rock (FeO(OH)·nH2O)

Synthetic Ruby (Jewel Bearings)

Synthetic Corundum (Al2O3 doped with Chromium)