Uncut Black Sapphire Tradeskill Recipes for 300 - 350
Uncut Black Sapphires are one of the many different gems added into the game during the Prophecy of Ro expansion and have an extremely low chance (probably around .05%) of dropping off basically any enemy in the game 30 - 90. Due to this, farming a specific location for this gem is impossible.
There's only a single recipe for us to learn that counts towards Jewelcrafting 300 - 350 for this item, the recipe is Square Cut Black Sapphire with a trivial of 300. One thing worth mentioning about this recipe is that it makes one of the most straight forward routes possible for raising JC to 300.
If you play more than one character or for some reason think you'll need to raise Jewelcrafting in the future from 1 - 300 keep Uncut Black Sapphires in mind. Or, do yourself an even larger favor and glance over my 1 - 300 Prophecy of Ro JC guide for a list of all the cheapest recipes you can do 1 - 300. All of the recipes mentioned on that page we're going to need to complete anyway to reach 350.
Jewelcrafting Uncut Black Sapphire Recipes (1 Recipe)