Loose faceted stone consistent with smoky quartz or glass

This item is a loose, faceted stone featuring an emerald-cut or rectangular step-cut geometry with clipped corners. It exhibits an opaque to translucent dark charcoal or smoky gray color. The surface shows notable wear and damage, including several pits across the table and significant abrasions/flea bites along the facets and girdle edges, which may suggest a lower hardness consistent with glass or quartz-based materials rather than harder gemstones like sapphire or diamond. Visible bubbles or surface inclusions are present, which are often characteristic of synthetic glass or certain silicate minerals. The owner notes it was originally set in a 10K gold band (unverified by image), which was a common mounting for mid-20th-century costume or semi-precious jewelry. Without professional gemological testing (refractive index, specific gravity, or microscopic inspection), the exact mineral species cannot be determined; however, it is stylistically consistent with decorative glass or smoky quartz common in vintage utility jewelry. No maker's marks or laser inscriptions are visible on the stone itself.

Based on my visual examination of the provided photograph, I have analyzed this loose, faceted stone. The item exhibits characteristics consistent with smoky quartz or dark glass, specifically noting the visible surface pitting and significant abrasions on the girdle and facets. These wear patterns suggest a lower Mohs hardness than precious gems like sapphire. The owner states the stone was originally set in a 10K gold band, which is typical for mid-20th-century costume or semi-precious jewelry, but I cannot verify the metal content or the stone's chemical composition from an image alone. Professional gemological testing, such as a refractive index or specific gravity test, would be required to determine the exact mineral species. The current estimate is based on the hypothesis that the stone is synthetic glass or a low-grade smoky quartz. In the current market, loose stones of this type with notable condition issues possess decorative rather than investment value. If the stone were identified as a more desirable material, such as natural untreated smoky quartz in pristine condition, the value might slightly increase. Conversely, if identified as modern mass-produced plastic or resin, the value would be negligible. To finalize an appraisal, an in-person inspection by a certified gemologist is necessary to assess the stone's internal structure and durability.