Seed pearls, small round and nearly round pearls generally less than 2mm in diameter, have been used in jewellery for a long time but became popular in the 18th and 19th centuries. Seed pearls were used to provide a border for a jewel or miniature, for tassels, to encrust a piece in pretty patterns or to imitate a cluster of grapes. They were used for sentimental jewellery.
When Queen Victoria entered her decades long mourning for Prince Albert, seed pearls were still used for borders around mourning brooches, rings and pendants as they symbolized teardrops of sadness. A growing middle class also meant that seed pearls could be used for more affordable jewellery.
Between 1840 to 1860, jewellery comprised completely of seed pearls was very popular. Seed pearl suites with created with a necklace, two bracelets, two earrings, a brooch and a corsage. The work was extremely time intensive and needed good eyesight and good light. The way the pieces of jewellery were constructed was to cut out a pattern on a thin plate of mother-of-pearl. The mother-of-pearl plate was then pieced to show where the seed pearls were to be attached. And then the pearls were attached using white horsehair. Horsehair from a living horse was used as it was finer than normal silk thread. When the threading was completed, the fittings were attached. The smallest seed pearls came drilled in bunches from China, slightly larger ones from India. The pearls were both sea and river pearls.
Half pearls in antique jewellery were small pearls that either had been cut away from the shell of the mussel and so had a flat side or were the better halves of defective pearls. They ranged in size from .5 mm to .75mm, up to 4mm in some cases. The centre of the half pearl industry was Idar and in Oberstein in the Duchy of Oldenburg, Germany. Pearls were purchased from India. In the Idar region alone, over 100 workers were employed. Half pearls were used in particular in lockets, watches and as borders for brooches.
Today, mabe or blister pearls are often referred to as half pearls but they are larger, and were grown against the shell wall and not in the tissue.