These antique mirror-cut diamond earrings were made in Belgium around 1850, set with table-cut diamonds in 18 karat gold. The so-called spread table or mirror-cut stones, with a large tabletop facet and a pavilion bottom, were cut from shallow Indian diamond crystals, to retain as much weight as possible. At the time these earrings were made, diamonds were still rarer. After the 1867 discovery of diamonds in South Africa, the supply of diamonds increased to more than a tenfold in the following ten years.

I wrote on the ‘herbarium’ label of these antique mirror-cut diamond earrings is RANUNCULUS REPENS or buttercup. Still, I’m not sure in determining this flower with the unusual amount of six petals, as it can be a jewellers fantasy.
Usually, buttercups have five petals, but with six or more it’s getting more interesting; counting the buttercups with additional petals is after all a reliable method to estimate the age of grasslands.

Link for more information and about buttercups with more than five petals.