Mineral Pseudomorph

Milky Quartz Mineral

Quartz (Silicon Dioxide, SiO2)

Mixed Mineral Specimens

Mixed Silicates, Oxides, and Phosphates (SiO₂, Ca₅(PO₄)₃(F,Cl,OH), Na₈Al₆Si₆O₂₄Cl₂, etc.)

Gneiss

Gneiss

Gneiss (specifically Granitic Gneiss)

Gneiss (composed primarily of Quartz, Feldspar, and Biotite/Amphibole)

Gneiss

Gneiss

Granite

Granite (Felsic Plutonic Rock)

Coarse-grained Granite

Granitoid (KAlSi3O8 + SiO2 + NaAlSi3O8)

Gneiss

Gneiss (High-grade metamorphic rock composed primarily of Quartz, Feldspar, and various Micas)

Gneiss

Banded Gneiss

Gneiss

Metamorphic Gneiss

Gneiss (with Quartzite and Mica)

Gneiss

Banded Gneiss

Gneiss (High-grade regional metamorphic rock)

Gneiss

Gneiss (High-grade Regional Metamorphic Rock)

Diorite

Phaneritic plutonic rock (dominated by plagioclase feldspar and hornblende)

Note: Item is not a geological specimen

n/a

Limonite (Iron Ore)

Hydrated iron(III) oxide-hydroxide (FeO(OH)·nH2O)

Lepidolite

K(Li,Al)3(Si,Al)4O10(F,OH)2

Gold Ore

Native Gold (Au) in Quartz or Silicate matrix

Desert Rose

Gypsum (variety Selenite) or Barite: CaSO4 · 2H2O

Turquoise in Matrix

CuAl6(PO4)4(OH)8·4H2O (Hydrous phosphate of copper and aluminium)

Limonite / Goethite (Ironstone)

Hydrated Iron(III) Oxide-Hydroxide FeO(OH)wnH2O

Schist with Biotite and Quartz

Biotite-Quartz Schist (Fe,Mg,Al silicate mix)

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.

Quartz Geode

SiO2 (Silicon Dioxide)

Turquoise and Hematite

CuAl6(PO4)4(OH)8·4H2O (Turquoise) and Fe2O3 (Hematite)

Red Sandstone (Iron-rich)

Ferruginous Sandstone (SiO2 with Iron Oxides)

Quartz-veined Sedimentary Rock

Hydrothermally veined Clastic Sedimentary Rock (SiO2 veins in Matrix)

Sandstone (likely with Quartz Veining)

Arenite (primarily SiO2)

Sandstone

Arenite (lithic or quartz sandstone)

Quartz Pebble

Silicon Dioxide (SiO2)

Calcite

Calcite (CaCO3)

Amethyst (with Pyrite and other minerals)

Silicon Dioxide (SiO2)

Fluorite (Rainbow/Purple Fluorite)

Calcium Fluoride (CaF2)

Orthoclase Feldspar

KAlSi3O8 (Potassium Aluminum Silicate)

Milky Quartz

Silicon Dioxide (SiO2)

Fluorite

Calcium Fluoride (CaF2)

Shale

Laminated Mudstone

Milky quartz (likely quartz-rich rock)

Quartz, silicon dioxide (SiO₂)

Milky quartz

Quartz (silicon dioxide, SiO₂)

Milky quartz

Quartz (silicon dioxide, SiO₂)

Quartz Pebble

Silicon Dioxide (SiO2)

Tumbled milky quartz

Quartz (SiO₂), likely massive milky quartz