Mineral/gemstone imitation

Rhinestone (or glass crystal)

Silicon dioxide (if glass) / Various

Clear, faceted, high luster, brittle. Hardness varies depending on material (glass is typically 5.5-7 on Mohs scale).

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Physical properties

Clear, faceted, high luster, brittle. Hardness varies depending on material (glass is typically 5.5-7 on Mohs scale).

Manufactured. Typically cast or cut from glass, lead crystal, or acrylic to imitate diamonds or other gemstones.

Used primarily in costume jewelry, clothing embellishment, and crafts.

Historically, rhinestones were rock crystals gathered from the river Rhine (hence the name). Today, they are mass-produced from glass or polymers.

Identify by uniform facets, possible foil backing, lack of inclusions common in natural stones, and lower refractive index compared to diamond.

Howlite (dyed)

Calcium borosilicate hydroxide (Ca2B5SiO9(OH)5)

Polished dendritic agate or jasper cabochon

Microcrystalline quartz, SiO₂, likely chalcedony with iron/manganese oxide inclusions

Diamond ring

Diamond (crystalline carbon, C)

Green polished gemstone (likely chrysoprase or aventurine)

Chrysoprase: microcrystalline quartz, SiO₂, colored by nickel; possible aventurine quartz: SiO₂ with fuchsite mica

Tumbled green gemstone, likely dyed howlite or serpentine

Most consistent with dyed howlite (Ca2B5SiO9(OH)5); exact identification requires testing

Turquoise (possible Howlite imitation)

Hydrated phosphate of copper and aluminium (CuAl6(PO4)4(OH)8·4H2O)