12x10mm Citrine Quartz: Quartz is a gemstone crystal, quite tough, and is the benchmark in gemstone toughness, anything less tough considered less durable, anything tougher considered just that, seriously tough and durable.
Naturally yellow Quartz is rare, and nowadays most Citrine Quartz on the market is heat-treated lilac Amethyst Quartz. The gemstones in these stud-eardrops were cut in Jaipur Rajasthan around 1980 and were said at the time to be naturally coloured. Certainly the colour of these two gemstones is excellent, more vibrant than most of what is available currently (anno 2023).