A MIRACLE OF NATURE
The Five Virtues of Pearls are an international standard which is used to assess value.
White South Sea Pearls are known for their large size and their soft, luxurious luster. They come in a variety of colors, depending on the oyster species and the environment they live in. The 'white-lipped' South Sea variety yields mainly colors in white, pink, silver and blue while the 'yellowlipped' variety grows Pearls from cream to yellow including champagne and gold. The natural golden colour is said to be the rarest.
A Pearl can double in price from one millimeter size to the next. For example a 12mm Perfect South Sea Pearl may be $1,000 and a 13mm Pearl with exactly the same characteristics might be $2,000 the increase in one mm in size literally makes that much difference.
There are so many variations within these categories that affect Pearl value however this is a very helpful "guide"