Rock Identifier

Category

Mineraloid (Cryptocrystalline Quartz)

Browse mineraloid (cryptocrystalline quartz) specimens identified by the Rock Identifier community.

Learn about Mineraloid (Cryptocrystalline Quartz) in the encyclopedia

Chalcedony

Black Onyx

Landscape Agate

Landscape Agate

Tube Agate

Sweetwater Agate

Sweetwater Agate

Frost Agate

Coldwater Agate

Honey Agate

Zebra Agate

Flame Agate

Feather Agate

Cathedral Agate

Cathedral Agate

Red Jasper (Jasper (a variety of Chalcedony, SiO₂)) — Mineraloid (cryptocrystalline quartz)

Red Jasper

Jasper (a variety of Chalcedony, SiO₂)

Mineraloid (cryptocrystalline quartz)

Limonite or Ironstone Nodule (FeO(OH)·nH2O (Hydrated iron(III) oxide-hydroxide)) — sedimentary

Limonite or Ironstone Nodule

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

Limonite/Goethite on Shale (Hydrous ferric oxides (FeO(OH)·nH2O) often associated with argillaceous rock) — sedimentary

Limonite/Goethite on Shale

Hydrous ferric oxides (FeO(OH)·nH2O) often associated with argillaceous rock

Obsidian (black volcanic glass), possibly slag or basalt (Obsidian; chiefly amorphous volcanic silica glass, approximately SiO₂-rich rhyolitic composition) — igneous

Obsidian (black volcanic glass), possibly slag or basalt

Obsidian; chiefly amorphous volcanic silica glass, approximately SiO₂-rich rhyolitic composition

Obsidian (Volcanic glass (mainly SiO2 with inclusions)) — igneous

Obsidian

Volcanic glass (mainly SiO2 with inclusions)

Snowflake Obsidian (Spherulitic Volcanic Glass (primarily SiO2 with Cristobalite inclusions)) — igneous

Snowflake Obsidian

Spherulitic Volcanic Glass (primarily SiO2 with Cristobalite inclusions)

Limonite (Iron Ore) (Hydrous ferric oxides (FeO(OH)·nH2O)) — mineral

Limonite (Iron Ore)

Hydrous ferric oxides (FeO(OH)·nH2O)

Snowflake Obsidian (Spherulitic Volcanic Glass (primarily SiO2)) — igneous

Snowflake Obsidian

Spherulitic Volcanic Glass (primarily SiO2)

Pink opal (Common opal, hydrated amorphous silica (SiO₂·nH₂O), commonly colored by trace organic or iron compounds) — mineral

Pink opal

Common opal, hydrated amorphous silica (SiO₂·nH₂O), commonly colored by trace organic or iron compounds

Limonite (Ironstone) Concretion (FeO(OH)·nH2O (Hydrous ferric oxide)) — sedimentary

Limonite (Ironstone) Concretion

FeO(OH)·nH2O (Hydrous ferric oxide)

Snowflake Obsidian (Flower Jasper variant) (Vitreous volcanic silicate with cristobalite inclusions) — igneous

Snowflake Obsidian (Flower Jasper variant)

Vitreous volcanic silicate with cristobalite inclusions

Small yellow-orange mineral fragment, likely amber or iron-stained quartz (Possibly amber (fossilized resin; organic mineraloid) or quartz (SiO₂)) — mineral

Small yellow-orange mineral fragment, likely amber or iron-stained quartz

Possibly amber (fossilized resin; organic mineraloid) or quartz (SiO₂)

Common Opal (SiO2·nH2O (Hydrated Silicon Dioxide)) — mineraloid

Common Opal

SiO2·nH2O (Hydrated Silicon Dioxide)

Cullet Glass (Slag) (Amorphous Silicon Dioxide (Man-made)) — Mineraloid

Cullet Glass (Slag)

Amorphous Silicon Dioxide (Man-made)

Common Opal in Host Rock (Hydrated Silica (SiO2·nH2O)) — mineraloid

Common Opal in Host Rock

Hydrated Silica (SiO2·nH2O)

Green Opal or Yellow Opal (Hydrated Silica (SiO2·nH2O)) — mineraloid

Green Opal or Yellow Opal

Hydrated Silica (SiO2·nH2O)

Snowflake Obsidian (Volcanic Glass with Cristobalite inclusions (70–75% SiO2)) — Igneous

Snowflake Obsidian

Volcanic Glass with Cristobalite inclusions (70–75% SiO2)

Limonite and Goethite (Ironstone) (Hydrous Iron Oxide Mixture (FeO(OH)·nH2O)) — sedimentary

Limonite and Goethite (Ironstone)

Hydrous Iron Oxide Mixture (FeO(OH)·nH2O)

Ethiopian Opal (Welo Opal) (Hydrated Amorphous Silica (SiO2·nH2O)) — mineraloid

Ethiopian Opal (Welo Opal)

Hydrated Amorphous Silica (SiO2·nH2O)

Pink Opal (Hydrated Amorphous Silica (SiO2·nH2O)) — mineraloid

Pink Opal

Hydrated Amorphous Silica (SiO2·nH2O)

Snowflake Obsidian (Spherulitic Obsidian (primarily SiO2 with Cristobalite inclusions)) — igneous

Snowflake Obsidian

Spherulitic Obsidian (primarily SiO2 with Cristobalite inclusions)

Opal (Hydrated Amorphous Silica (SiO2·nH2O)) — mineral

Opal

Hydrated Amorphous Silica (SiO2·nH2O)

Pink Opal (Hydrated Silicon Dioxide (SiO2 · nH2O)) — mineraloid

Pink Opal

Hydrated Silicon Dioxide (SiO2 · nH2O)

Precious Opal (Hydrated silica (SiO2·nH2O)) — mineraloid

Precious Opal

Hydrated silica (SiO2·nH2O)

Green Opal (Hydrated Silica (SiO2·nH2O)) — mineraloid

Green Opal

Hydrated Silica (SiO2·nH2O)

Polished black obsidian (Volcanic glass; predominantly rhyolitic silica glass (approximately 70–80% SiO₂)) — igneous

Polished black obsidian

Volcanic glass; predominantly rhyolitic silica glass (approximately 70–80% SiO₂)

Tumbled mahogany obsidian (Volcanic glass; primarily SiO₂ with iron-oxide-rich brown inclusions) — igneous

Tumbled mahogany obsidian

Volcanic glass; primarily SiO₂ with iron-oxide-rich brown inclusions

Sea Glass (Frosted Quartz/Glass) (Amorphous Silicon Dioxide (SiO2)) — Mineraloid

Sea Glass (Frosted Quartz/Glass)

Amorphous Silicon Dioxide (SiO2)

Black Opal (Triplet) (Hydrated Silica (SiO2·nH2O)) — mineral

Black Opal (Triplet)

Hydrated Silica (SiO2·nH2O)

Amber (Succinite (a specific common type) or Fossilized Tree Resin (C10H16O)) — Mineraloid

Amber

Succinite (a specific common type) or Fossilized Tree Resin (C10H16O)

Black Obsidian (Obsidian (Volcanic Glass)) — igneous

Black Obsidian

Obsidian (Volcanic Glass)

Snowflake Obsidian (Volcanic Glass with Spherulite Inclusions (primarily SiO2)) — igneous

Snowflake Obsidian

Volcanic Glass with Spherulite Inclusions (primarily SiO2)

Snowflake Obsidian (Volcanic glass with Cristobalite inclusions (mostly SiO2)) — igneous

Snowflake Obsidian

Volcanic glass with Cristobalite inclusions (mostly SiO2)

Snowflake Obsidian (Volcanic glass (SiO2 - Silicon Dioxide with Cristobalite inclusions)) — igneous

Snowflake Obsidian

Volcanic glass (SiO2 - Silicon Dioxide with Cristobalite inclusions)

Snowflake Obsidian (Spherulitic Volcanic Glass (SiO2 + impurities)) — igneous

Snowflake Obsidian

Spherulitic Volcanic Glass (SiO2 + impurities)

Limonite (Iron Ore) (Limonite (an FeO(OH)·nH2O mineraloid, not a true mineral due to variable composition)) — Mineral

Limonite (Iron Ore)

Limonite (an FeO(OH)·nH2O mineraloid, not a true mineral due to variable composition)

Obsidian (likely black volcanic glass) (Obsidian; primarily amorphous volcanic silica glass, approximately SiO₂-rich rhyolitic composition) — igneous

Obsidian (likely black volcanic glass)

Obsidian; primarily amorphous volcanic silica glass, approximately SiO₂-rich rhyolitic composition

Black obsidian (Volcanic glass; predominantly silica-rich, noncrystalline SiO₂) — igneous

Black obsidian

Volcanic glass; predominantly silica-rich, noncrystalline SiO₂

Red Sandstone (Clastic Sedimentary Mineraloid (predominantly Quartz grains with Iron Oxide cement)) — sedimentary

Red Sandstone

Clastic Sedimentary Mineraloid (predominantly Quartz grains with Iron Oxide cement)

Precious Opal (Hydrated Silicon Dioxide (SiO2·nH2O)) — gemstone

Precious Opal

Hydrated Silicon Dioxide (SiO2·nH2O)

Limonite with Quartz (Gossan) (Hydrated iron(III) oxide-hydroxide mixture (FeO(OH)·nH2O) with Silicon Dioxide (SiO2)) — Mineral

Limonite with Quartz (Gossan)

Hydrated iron(III) oxide-hydroxide mixture (FeO(OH)·nH2O) with Silicon Dioxide (SiO2)

Mahogany Obsidian (Volcanic glass (SiO2 + Fe2O3)) — igneous

Mahogany Obsidian

Volcanic glass (SiO2 + Fe2O3)