Amethyst
Amethyst (Silicon Dioxide - SiO2 with iron impurities)
mineral
Category
Igneous Or Sedimentary
Browse igneous or sedimentary specimens identified by the Rock Identifier community.
Learn about Igneous Or Sedimentary in the encyclopedia
View all →
Specular Hematite
Hematite (Fe2O3)
mineral
Gneiss
High-grade Metamorphic Gneiss
metamorphic
Banded Gneiss
Gneiss (High-grade metamorphic rock)
metamorphic
Gneiss
Gneiss
metamorphic
Banded gneissic rock
Gneiss, likely quartz–feldspar–biotite gneiss
metamorphic
Gneiss
Metamorphic Gneiss
metamorphic
Banded gneiss (possibly migmatitic gneiss)
Quartz–feldspar–mica gneiss; composition commonly includes quartz, feldspar, biotite/hornblende, and accessory dark minerals
metamorphic
Foliated Gneiss (River-Worn Pebble)
Gneiss (High-grade Regional Metamorphic Rock)
metamorphic
Quartz Geode (Nodule)
Silicon Dioxide (SiO2)
sedimentary or igneous
Tree Agate
Dendritic Agate (Silicon Dioxide, SiO2)
mineral
Banded Gneiss
Gneiss (High-grade regional metamorphic rock)
metamorphic
Feldspathic Gneiss
Feldspathic Gneiss (High-grade regional metamorphic rock)
metamorphic
Banded Gneiss
Gneiss (High-grade metamorphic rock)
metamorphic
Druzy Quartz (on Geode Fragment)
Silicon Dioxide (SiO2)
mineral
Banded gneiss or banded metamorphic rock
Gneiss, likely quartz–feldspar–biotite gneiss
metamorphic
Gneiss
Foliated Metamorphic Rock (Gneiss)
metamorphic
Blue-dyed Quartz Druzy
Silicon Dioxide (SiO2) with artificial pigment
mineral
Amethyst
Amethyst (SiO2 - Silicon Dioxide with iron impurities)
mineral
Banded Gneiss
Gneiss (High-grade Regional Metamorphic Rock)
metamorphic
Brown Chalcedony (Agate/Jasper blend)
Silicon dioxide (SiO2)
sedimentary
Banded gneiss pebble
Gneiss, commonly quartz–feldspar–mica gneiss
metamorphic
Banded Gneiss
Gneiss (High-grade Regional Metamorphic Rock)
metamorphic
Yellow Chalcedony (Carnelian/Yellow Agate)
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Mineral
Gneiss with Quartz Vein
Gneiss (containing SiO2 vein)
metamorphic
Carnelian (Tumbled)
Carnelian (Chalcedony / Silicon Dioxide, SiO2)
mineral
Dendritic Opal (Common Opal)
Amorphous Hydrated Silica (SiO2·nH2O) with Manganese or Iron Oxide inclusions
mineral
Banded gneiss pebble
Biotite–quartz–feldspar gneiss (composition variable)
metamorphic
Banded Gneiss
Gneiss (Metamorphic Rock)
metamorphic
Gneiss (specifically a weathered or stream-worn specimen)
Gneiss (Foliated Metamorphic Rock)
metamorphic
Gneiss
Gneiss (High-grade regional metamorphic rock)
metamorphic
Banded Gneiss
Gneiss (Metamorphic high-grade rock)
metamorphic
Gneiss
Gneiss (High-grade metamorphic rock typically composed of Quartz, Feldspar, and Mica/Amphibole)
metamorphic
Banded gneiss pebble
Gneiss, likely quartz–feldspar–mica gneiss
metamorphic
Agate Geode
Chalcedony (SiO2 - Silicon Dioxide)
sedimentary (secondary mineral formation)
Quartz Geode Fragment
Silicon Dioxide (SiO2)
mineral
Gneiss
Metamorphic Gneiss
metamorphic
River Cobble (Gneiss/Migmatite)
Gneissic Metamorphic Rock (composed mainly of Quartz, Feldspar, and Biotite)
metamorphic
Quartz (Milky/Gravel variety)
Silicon Dioxide (SiO2)
mineral
Weathered gneissic metamorphic rock
Gneiss, likely quartz–feldspar–mica gneiss
metamorphic
Mixed river-worn rock and mineral collection
Mostly quartz/quartzite, feldspar-bearing granitoid, chert, and mafic volcanic rocks; exact species vary by pebble
igneous, sedimentary, metamorphic, mineral
Pink Opal / Peruvian Opal
Hydrated amorphous silicon dioxide (SiO2·nH2O)
Mineral