1) A lady’s morning dress should be simple and refined, and suited to the time of day. Neither is much jewellery consistent; plain gold and silver ornaments are permissible, but never precious stones, except in rings.
2) In the ball-room jewellery is generally worn in sets; ornaments never look so well if pieces of different sets are displayed together; that is to say, if diamonds are in the brooch, a necklet of pearls and earrings set with emeralds would not look well if worn on the same occasion. All the ornaments should match in character as much as possible, but variety is allowed in the matter of bracelets.
3) It is not considered good taste for a man to wear much jewellery. A plain, handsome ring, studs, and sleeve-links, a watch-chain without pendants, will always look more seemly than a great display of elaborate ornaments.
4) Brides do not wear much jewellery, especially when they are young girls.
5) At the opera, the full brilliancy of evening dress is seen, with tiaras or diamond stars or combs in every head, and a proportionate display of jewellery on the neck and dress.
Etiquette of Good Society by Lady Colin Campbell
Etiquette for Every Day by Mrs. Humphry