Polished pale chalcedony or quartz pebble
Microcrystalline quartz, SiO₂; possibly milky quartz/chalcedony
mineral
Category
Igneous And Sedimentary
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Amethyst
Amethyst (Silicon Dioxide - SiO2 with iron impurities)
mineral
Biotite-rich gneiss
Foliated quartz–feldspar–mica gneiss; mainly quartz, plagioclase/alkali feldspar, and biotite
metamorphic
Common Opal in Host Rock
Hydrated Silica (SiO2·nH2O)
mineraloid
Fancy Jasper
Agate (Silicon Dioxide, SiO2)
sedimentary
Labradorite-bearing gneiss or altered feldspathic rock
Plagioclase-rich gneiss, locally labradorescent; composition likely plagioclase feldspar, quartz, mica, and iron-oxide veining
metamorphic
Banded Gneiss
Gneiss (Metamorphic rock predominantly containing quartz, feldspar, and mica)
metamorphic
Banded Gneiss
Gneiss (Metamorphic high-grade rock)
metamorphic
Gneiss
Gneiss
metamorphic
Gneiss
Gneiss
metamorphic
Gneiss
Gneiss (Foliated Metamorphic Rock)
metamorphic
Botryoidal Chalcedony (Agate)
Silicon Dioxide (SiO2)
mineral
Banded Gneiss
Gneiss (Metamorphic silicate rock)
metamorphic
Gneiss (with Quartzite and Biotite)
Gneiss containing SiO2 (Quartz), K(Mg,Fe)3AlSi3O10(OH)2 (Biotite), and (K,Na,Ca)AlSi3O8 (Feldspar)
metamorphic
Botryoidal Chalcedony (Agate/Desert Rose Chalcedony)
Silicon Dioxide (SiO2) - Cryptocrystalline Quartz
mineral
Weathered metamorphic rock, likely gneiss or schist
Indeterminate foliated silicate rock; commonly quartz–feldspar–mica assemblage
metamorphic
Gneiss
Metamorphic Gneiss
metamorphic
Gneiss
Gneiss
metamorphic
Gneiss
Gneiss
metamorphic
Gneiss
Gneiss (High-grade Metamorphic Rock)
metamorphic
Banded Gneiss
Foliated Gneiss
metamorphic
Botryoidal Chalcedony (Agate)
Silicon Dioxide (SiO2)
mineral
Banded Gneiss (with Quartz Vein)
Gneiss (Metamorphic rock of varying mineralogy)
metamorphic
Gneiss
Gneiss
metamorphic
Gneiss
Gneiss
metamorphic
Quartz Druzy (on Calcedony/Quartz base)
Silicon Dioxide (SiO2)
mineral
Banded gneiss
Quartz–feldspar gneiss, possibly biotite-bearing; exact identification requires testing
metamorphic
Quartz on Host Rock
Silicon Dioxide (SiO2)
Mineral Specimen
Banded metamorphic rock, likely gneiss or amphibolite
Composition uncertain; probable quartz–feldspar–amphibole assemblage
metamorphic
Rounded river pebble, likely quartz-rich sandstone or fine-grained granite
Indeterminate from photograph; possible quartz/feldspar-bearing granitic pebble
igneous
Likely blue-gray gneiss
Gneiss, a foliated metamorphic rock; exact mineral composition cannot be confirmed from the image
metamorphic
Polished blue-gray stone, likely labradorite or gneiss
Labradorite-bearing gneiss; plagioclase feldspar-rich rock
metamorphic
Gneiss
High-grade Metamorphic Gneiss
metamorphic
Fluorite in Matrix
Calcium Fluoride (CaF2) with Quartz/Calcite matrix
mineral
Gneiss
Gneiss (High-grade metamorphic rock)
metamorphic
Banded gneiss
Foliated silicate rock, typically quartz–feldspar–mica gneiss
metamorphic
Banded gneiss (likely amphibolite-rich gneiss)
Banded gneiss; composition commonly quartz, feldspar, mica and/or amphibole
metamorphic
Felsic Drill Core (likely Gneiss or Granite)
Felsic Metamorphic Rock (Gneissic profile)
metamorphic
Gneiss
Gneiss
metamorphic
Dendritic Agate
Silicon Dioxide (SiO2) with manganese/iron inclusions
mineral
Banded Agate (Agatized Geode Slice)
Silicon Dioxide (SiO₂)
mineral
Gneiss
Foliated Metamorphic Rock
metamorphic