Mineraloid Like Synthetic Material

Rough Emerald

Beryl (Be3Al2(SiO3)6 with Chromium/Vanadium impurities)

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.

Banded Chert (or Flint)

Microcrystalline Quartz (SiO2)

Chert (Flint Pebbles)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Sandstone (Pebble/Cobble)

Sandstone (arenite is a more precise term for sandstone with less than 15% matrix; this specimen appears to be a lithic or quartz arenite)

Diorite

Diorite (Intermediate intrusive igneous rock)

Obsidian

Volcanic glass

Peridot

Olivine ((Mg,Fe)2SiO4)

Limestone

Calcareous sedimentary rock (CaCO3)

Quartzite

Quartzite (SiO2)

Limestone

Calcium Carbonate (CaCO3)

Serpentinite

Serpentinite (composed primarily of Serpentine group minerals, (Mg,Fe,Ni,Al,Zn,Mn)2-3(Si,Al,Fe)2O5(OH)4)

Sandstone (Pebble)

Sandstone (arenite, arkose, wacke depending on composition)

Green Jasper (with Quartz veining)

Jasper (Silica-rich microcrystalline variety of Quartz), formula: SiO2

Chert (Yellow Jasper variant)

Microcrystalline Quartz (SiO2)

Chert (Flint)

Silicon Dioxide (SiO2)

Iron Meteorite

Iron-nickel alloy (primarily kamacite and taenite)

Scoria

Scoria (a vesicular basalt or andesite)

Chert (Flint variety)

Chert (Microcrystalline or Cryptocrystalline Quartz), SiO2

Basalt

Mafic Volcanic Rock (composed of Plagioclase Feldspar and Pyroxene)

Anthracite Coal

Anthracite

Quartzite

Quartzite (primarily SiO2)

Petrified Wood

Silicified Wood (SiO2)

Chert (Cherty Limestone or Flint)

Microcrystalline Silica (SiO2)

Quartz Vein in Siltstone

SiO2 (Quartz) on clastic sedimentary matrix

Diamond (in Jewelry)

Carbon (C)

Banded Chert

Cryptocrystalline Quartz (SiO2)

Diamond

Diamond (C)

Lapis Lazuli

Lapis Lazuli (a rock type, not a single mineral; main component is Lazurite (Na,Ca)8[(S,Cl,SO4,OH)2|(Al6Si6O24)])

Banded Chert (Flint)

Cryptocrystalline Quartz (SiO2)

Malachite

Malachite [Cu2CO3(OH)2]

Labradorite

Labradorite ((Ca, Na)(Al, Si)4O8)

Chert (often called Flint when dark)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Sandstone (specifically Arkose or Quartz Arenite)

Arenite (primarily SiO2 with possible Feldspar)

Petrified Wood

Silicified Wood (SiO2)

Concrete / Anthropogenic Conglomerate

Man-made composite material (Portland cement, aggregate, and water)

Sandstone

Quartz Sandstone (predominantly)

Chert (Nodule)

Microcrystalline Quartz (SiO2)

Pyrite (Fool's Gold)

Iron Disulfide (FeS2)

Diamond (Emerald Cut)

Carbon (C)

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Asphalt (Bituminous Concrete)

Asphaltum / Bitumen-Aggregate Matrix