Some examples of jewelry from the 18th century:
Stomacher brooch, early 18th century
France
Les Arts Décoratifs, Paris
Magdaleine Pinceloup de la Grange, née de Parseval, by Jean-Baptiste Perronneau, 1747
Oil on canvas, 65.1 × 52.4 cm
J. Paul Getty Museum, Los Angeles
Lady Mary Wortley Montagu, by Joseph Highmore, before 1762
oil on canvas, 76cm x 61.5cm
Private collection
Portrait of a lady, traditionally identified as Ann Burney, attributed to James Wills, 1740-1777
76.5 x 63.5 cm
Shoe buckles, c. 1750 – 1760
City of Paris
Pair of earrings, c. 1760
probably Italian
Private collection
Ulrike Sophie of Mecklenburg, by Georg David Matthieu, 1765
oil on canvas, 145 x 105 cm
Staatliches Museum Schwerin, Germany
Paula Melzi d’Eril, by Francisco Bayeu, 1770-1775
Spain
Detail, ?
Chrysler Museum of Art, Virginia
Group of 18th century paste jewellery
Private collection
Archduchess Maria Amalia of Austria (future Duchess of Parma), by unknown artist, second half 18th century
If you know about missing informations of origin or copyright please let me know!