Mineral And Organic Gemstone

Eudialyte in Matrix

Na15Ca6Fe3Zr3Si26O72(OH,Cl,H2O)3

Carnelian

Carnelian (Silicon Dioxide, SiO2)

Limonite after Pyrite (Prophecy Stone)

Limonite (FeO(OH)·nH2O) replacing Pyrite (FeS2)

Pyrite in Shaly Matrix

Iron Sulfide (FeS2)

Chert (White Chert / Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Petrified Wood

Silicified Wood (primarily SiO2)

Petrified Wood

Silicified Wood (primarily SiO2)

Chert (often called Flint)

Microcrystalline to cryptocrystalline quartz (SiO2)

Petrified Wood

Silicified Wood (primarily SiO2)

Chrysocolla on Quartz/Rhyolite matrix

Hydrated copper phyllosilicate mineral: (Cu,Al)2H2Si2O5(OH)4·nH2O

Fossiliferous Limestone

Biogenic Limestone (Calcium Carbonate, CaCO3)

Chert (Jasper/Flint variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Moss Agate

Silicon Dioxide (SiO2) with inclusions of Manganese or Iron oxide

Fossilized Horn Coral

Order Rugosa (Rugose Coral)

Amber / Copal

Organic resin, C10H16O

Chert (Arrowhead Preform or Flake)

Microcrystalline Quartz (SiO2)

Sodalite

Na8(Al6Si6O24)Cl2 (Sodium Aluminum Silicate Chloride)

Chert (Nodule)

Silicon Dioxide (SiO2)

Sandstone

Arenicola (comprising mostly Quartz, SiO2)

Mother of Pearl (Nacre)

Calcium Carbonate (primarily aragonite, with conchiolin)

Larimar

Blue Pectolite (NaCa2Si3O8(OH))

Quartz (Milky/Rose variety)

Silicon Dioxide (SiO2)

Pearl

Calcium Carbonate (primarily Aragonite and Calcite), CaCO3

Chert (and Chert-based Jasper)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Given the appearance, it's likely a fragment of an igneous or metamorphic rock composed of multiple minerals. Without specific diagnostic features, it's difficult to give a common name other than 'crystalline rock fragment'. If pressed to guess based on the granular, somewhat light and dark speckled appearance, it could be a fragment of granite or a related intrusive igneous rock.

As a rock fragment, it does not have a single scientific mineral name; rather, it's a piece of a rock which is a combination of minerals. If it were granite, its main mineral composition would be quartz (SiO2), feldspar (e.g., KAlSi3O8 - orthoclase, (Na,Ca)(Al,Si)4O8 - plagioclase), and mica (e.g., KAl2(AlSi3O10)(OH)2 - muscovite or K(Mg,Fe)3AlSi3O10(OH)2 - biotite), among others.

Pink Tourmaline (Rubellite) in Lepidolite

Elbaite (Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)4) in Lepidolite (K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2)

Puddingstone (Jasper-Conglomerate)

Conglomerate (Silicon Dioxide, SiO2 with impurities)

Lepidolite

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

Quartz Vein in Host Rock

Silicon Dioxide (SiO2) within a metamorphic matrix

Petrified Wood

Silicified Wood (primarily Silicon Dioxide, SiO2)

Amber (Rough)

Amber (Fossilized Tree Resin, succinite)

Citrine

SiO2 (Silicon Dioxide)

Petrified Wood

Silicified Wood (SiO2)

Nacre (Mother of Pearl)

Nacre (Biogenic Aragonite/Calcite composite, CaCO3)

Chert (Chalcedony)

Silicon Dioxide (SiO2)

Chert / Flint

Microcrystalline or cryptocrystalline quartz (SiO2)

Petrified Wood

Silicified Wood (SiO2 as Quartz/Chert/Chalcedony)

Chert (Brown Variety)

Silicon dioxide (SiO2)

Pyrite Geode

Iron Disulfide (FeS2)

Moss Agate

Silicon Dioxide with inclusions (SiO2 + impurities)

Pyrite

Iron Sulfide (FeS2)

Petrified Wood

Silicified wood (Quartz, Chalcedony, or Opal)