Petoskey Stone (Petrified Favosites)
Favosites (extinct colonial coral), CaCO3 with Silica replacement
sedimentary
Category
Mineral (Biogenic Replacement)
Browse mineral (biogenic replacement) specimens identified by the Rock Identifier community.
Chert
Chert (microcrystalline quartz)
Sedimentary
Jasper
Chalcedony (cryptocrystalline quartz), SiO2
Sedimentary
Chert / Flint (a variety of Chert)
Chert (SiO2)
Sedimentary Rock (technically a microcrystalline quartz mineral aggregate)
Chert (or Flint)
Chert (a cryptocrystalline variety of quartz, SiO2)
sedimentary
Tiger's Eye
Silicon dioxide (SiO2) with fibrous inclusions of crocidolite (riebeckite) that have been altered to limonite and then replaced by quartz
Mineral
Pebble (likely Quartz or Chert)
SiO₂ (Silicon Dioxide) - referring to the likely main mineral composition, Quartz. If it's chert, the scientific name remains SiO₂ with a microcrystalline structure.
Sedimentary Rock
Chert (Flint)
Chert (predominantly SiO₂ - silicon dioxide)
sedimentary
Leopard Skin Jasper
Chalcedony (cryptocrystalline quartz) with inclusions
Mineral
Chert (varieties include Flint or Jasper)
Chert (cryptocrystalline quartz; SiO₂)
Sedimentary
Red Jasper or Chert
Jasper (SiO2, a variety of chalcedony with iron oxide impurities), Chert (SiO2)
sedimentary
Turquoise
Turquoise (CuAl6(PO4)4(OH)8·4H2O)
mineral
Chert / Flint
Chert (varieties include Flint)
Sedimentary
Mixed Chalcedony and Jasper Bracelet (possibly 'Ocean Jasper' or similar banded variety for brown beads, and blue/grey Chalcedony for the translucent beads)
Chalcedony (SiO2), Jasper (SiO2 with impurities)
Mineral (specifically a cryptocrystalline variety of Quartz)
Chert (often referred to as 'Jasper' when red)
Chert (microcrystalline quartz, SiO₂)
Sedimentary rock
Wood Jasper
Siliceous sedimentary rock (variety of Chert/Chalcedony)
Sedimentary
Pyrite
Pyrite (Iron sulfide, FeS₂)
mineral
Fuchsite
Chromium-rich Muscovite (KAl2(AlSi3O10)(OH,F)2 with Cr replacements)
mineral
Blue Chalcedony and Picture Jasper Beads
Blue Chalcedony (SiO2), Picture Jasper (SiO2)
Mineral
Black Chert
Chert (microcrystalline quartz)
Mineral
Chert (or Flint)
Silicon dioxide (SiO2)
sedimentary
Red Jasper (beads)
Silicon Dioxide (SiO2) with iron inclusions
Sedimentary Rock
Chert Pebble/Nodule
Chert (a microcrystalline or cryptocrystalline sedimentary form of quartz, SiO2)
Sedimentary
Chert (variant of Flint)
Chert (SiO2)
Sedimentary
Chert (Jasper Variant likely)
Silicon Dioxide (SiO2)
Sedimentary Rock or Mineral (depending on origin and purity)
Tiger's Eye (Brown/Gold variety)
Pseudomorph of Quartz after Crocidolite (SiO2 with FeOOH inclusions)
metamorphic
Chert or Flint (polished/water-worn)
Chert (a microcrystalline or cryptocrystalline variety of quartz, SiO2). Flint is a specific variety of chert.
Sedimentary (most likely, as Chert is a sedimentary rock often found as nodules in limestone or as bedded deposits; however, it can also form by metasomatic replacement, which leans towards metamorphic processes under certain conditions)
Pearl
Calcium carbonate (CaCO3) - mainly Aragonite with Conchiolin
mineraloid
Pearl
Aragonite / Calcium Carbonate (CaCO3)
mineraloid
Pearl
Aragonite and Conchiolin (CaCO3 + organic protein)
mineraloid
Black Pearl (Tahitian Type)
Aragonite / Conchiolin composite (CaCO3)
mineraloid
Pearl (likely Freshwater or Akoya Cultured)
Aragonite / Conchiolin composite (CaCO3)
Mineralloid (Organic gemstone)
Pearl (Imitation or Cultured)
Calcium Carbonate (Aragonite/Calcite) - CaCO3
Mineraloid (Organic)
Cat's Eye Shell (Shiva Shell)
Operculum of the Turbo petholatus (Tapestry Turban Snail), predominantly Calcium Carbonate (Aragonite)
mineraloid / biogenic specimen
Shell Cameo
Cypraecassis rufa (Bullmouth Queen Helmet Shell)
mineraloid / biogenic specimen
Red Jasper
Quartz (Silicon Dioxide) with Iron Oxide impurities (Fe2O3)
mineralological specimen