Organic Gemstone (Often Associated With Sedimentary Sequences)

Yellow Jasper

Chalcedony (Silicon Dioxide, SiO2)

Chert (often called Flint when dark)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Pyrulite (Pyrite / Chalcopyrite)

Iron Sulfide (FeS2) or Copper Iron Sulfide (CuFeS2)

Red Coral

Corallium rubrum (for precious red coral), although other species like Corallium japonicum and Paracorallium are also used.

Quartz Geode

Silicon Dioxide (SiO2) within a secondary sedimentary structure

Chert (Iron-stained)

Microcrystalline Quartz (SiO2)

Quartz (Milky Quartz)

Silicon Dioxide (SiO2)

Gold-bearing Quartz with Pyrite

Quartz (SiO2) with Gold (Au) and Pyrite (FeS2)

Unakite

Unakite (an altered granite composed of Epidote, Orthoclase, and Quartz)

Lepidolite

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

Lepidolite

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

Howlite

Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)

Chert (Flint)

Microcrystalline Quartz (SiO2)

Greenstone (Epidosite or Altered Basalt)

Epidosite (Ca2(Al, Fe)3(SiO4)3(OH))

Moonstone

Adularia or Orthoclase (KAlSi3O8) or Albite (NaAlSi3O8), specifically with lamellar exsolution of albite and orthoclase.

Chert (often called Flint)

Silicon Dioxide (SiO2)

Amazonite

K(AlSi3O8) - Microcline variant

Rhodonite

Manganese Inosilicate (MnSiO3)

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (often called Flint or River Stone)

Chert (Microcrystalline Silicon Dioxide, SiO2)

Petrified Wood

Silicified Wood (primarily SiO2)

Chert (White Chert/Flint)

Chert (SiO2)

Chert (Jasper/Agate variety)

Microcrystalline Quartz (SiO2)

Petrified Wood

Silicified wood (Quartz, Chalcedony, or Opal)

Chert (River Pebble)

Microcrystalline Quartz (SiO2)

Chert (Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Coal (Anthracite)

Anthracite (Carbon-based organic sedimentary/metamorphic rock)

Serpentine

Antigorite, Lizardite, or Chrysotile (Mg,Fe,Ni,Al,Zn,Mn)2-3(Si,Al,Fe)2O5(OH)4

Lepidolite

K(Li,Al)3(Al,Si)4O10(F,OH)2 (Lithium-bearing phyllosilicate)

Red Chert (Jasper)

Microcrystalline Quartz (SiO2)

Malachite

Malachite (Cu2(CO3)(OH)2 - a copper carbonate hydroxide mineral)

Chert (Yellow Jasper variant)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Amazonite (likely mixed with other feldspars/minerals)

Amazonite is a variety of Microcline, which is a tectosilicate mineral, formula KAISi3O8. The mixed beads could include other feldspars or quartz.

Graphite

Graphite (Native Carbon, C)

Fluorite

Fluorite (Calcium Fluoride, CaF2)

Jasper (likely Brown or Brecciated)

Jasper (Silicon Dioxide, SiO2)

Quartz Geode

Silicon Dioxide (SiO2)

Septarian Nodule

Septarian Concretion (CaCO3 with Siderite/Limonite streaks)

Green Fluorite

Calcium Fluoride (CaF2)

Veined Quartz

SiO2 (Silicon Dioxide)

Chert Pebble

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Chert (Arrowhead Fragment)

Microcrystalline Quartz (SiO2)