Just from one picture my guess would be amber, but that is way older than 5200 years. In fact, most gemstones are far older. Next guess is citrine or garnet, or topaz. All come in large sizes. The general outline of the shape seems to show some worn geometry which, if not accidental, is a typical garnet crystal shape. Now garnet is my first guess because of the shape, but the crust looks a lot like that of amber.