Boulder Opal and Fire Opal are not specific terms enough to say, the mine or place it came from Nevada, Australia, Mexico Honduras or places like Ethiopia that I have zero experience with. but a few pounds from the same mine with a range of look can allow you to experiment with the worst of it and save the best for when you have an idea of what you are doing… looking for only the best pieces gets you the highest prices but actual “mine run” that has not been cherry picked over is best if you can get it.
I knew someone who was traveling in Thailand and absolutely was going to buy a ruby, would maybe buy a sapphire but probably not. Well, he got back with a Ruby a sapphire and a Bracelet that someone had pushed him to buy. The Ruby was a total rip not worth a quarter of what he paid, the Saphire was about stanrard expected price but the bracelet was worth way over what he paid and more than all he had purchased.