925 Sterling Silver - is one of the most popular metals used to make jewellery. Silver alone it is far too soft to be used everyday therefore is alloyed with other metals such as copper to increase its durability.
Gold Vermeil - is your next best option to solid gold. A thick gold coating (minimum 2.5 microns) is used over the top of a sterling silver (92.5% silver) base. The layer of gold in gold vermeil jewellery is 5 times thicker than gold plated jewellery. Since the base metal is always sterling silver – a precious metal in itself that is commonly used in fine jewellery, gold vermeil jewellery is inherently valuable and can last year and years.
Gold Plated (1 micron) on Sterling Silver base - Gold plating onto a sterling silver base, particularly with a 1 micron thickness, offers multiple benefits in jewellery-making. The combination of sterling silver and gold plating provides a luxurious appearance similar to solid gold jewellery at a more budget-friendly price. The 1 micron thickness ensures a robust and long-lasting finish, offering resistance to tarnishing and wear over time. Moreover, the sterling silver base is hypoallergenic, making it suitable for individuals with sensitive skin or metal allergies.
Gold Filled - is a mid-range type of gold jewellery that is covered in a layer of gold. The gold is adhered to the base metal mechanically by soldering or welding. The manufacturing costs are higher, which is partly why you’ll see higher prices on gold filled products, even if the base metal is only brass or copper. Gold filled jewellery is more strictly regulated than gold plated jewellery, though it doesn’t set quite the same standard as gold vermeil.
Gold Flash Plated - is essentially where a metal goes through a process called "electroplating" to cover a cheaper base metal such as copper or brass with a thin layer of gold to create its finished look. Gold plated pieces are a more affordable option but do have a short lifespan due to the coating eventually rubbing off.
Please see here for visual representation