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Recognising paste and imitation gems

Glass posing as gemstones — historic, clever, and collectable in its own right.

Imitation stones are ancient: the Romans imitated emeralds and carnelian in glass, and 18th-century 'paste' — brilliant-cut leaded glass, often foil-backed in closed settings — was worn proudly by the fashionable. Paste is not fraud by default; it is its own collected tradition.

Under a loupe, glass betrays itself: rounded facet edges where stone would be crisp, internal swirls and bubbles, moulding traces, and wear frosting on high points. Foil backing behind a stone in a closed-back setting is a strong paste signal. A thermal tester or refractometer settles hard cases, but honest description usually suffices.

Write what you observe — 'colourless faceted stone, rounded facet junctions, one visible bubble, closed foiled setting' — and let the conclusion stay probabilistic. The setting's metal and construction usually date the piece better than the stone does.

From the guide library inside Collectors Catalogues, a free app for cataloguing antiques and finds with honest, museum-grade records.

More on jewellery

Dating medieval brooches — Form, pin, and section are your clues.

Identifying brooch and fibula types — Spring, bow, and catch.

Identifying finger rings — Hoop, shoulders, and bezel.

Identifying beads — Material, perforation, and wear.

Identifying cameos and intaglios — Carved in relief or sunk.

Identifying earrings — Hoops, pendants, and wires from four thousand years of pierced ears.

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