A diamond is valued by its cut, clarity, carat weight and colour. A local jeweler experienced in diamond cutting can look at your stone and give you a precise answer.
Remember, about 60% of the stone's weight will be lost in cutting it into a gem shape.
Not generally, in the sense that raw colourless stones are transparent.
Black diamonds, properly Carbonado, are priced a little less than clear diamonds of the same carat weight.Your local jeweler may be able to show you black diamonds with prices.
Mexico is not known for its raw diamonds.
raw black tourmaline is worth about 50 usd per kg
Michigan is not known for its raw diamonds.
Black diamonds are black.
Antarctica is not known for its raw diamonds.
Any diamond is worth what someone will pay you for it. A black diamond is graded according to the classic four Cs of diamonds: cut, colour, clarity and carat weight. A raw diamond looses about 60% of its carat weight during the cutting process. You could find a diamond cutter willing to work with you to price and otherwise deal with your raw diamond.
You can buy black diamonds.
carbon
Raw diamonds are transported like any other valuable: heavily guarded, tightly secured and usually in secret.
Black diamonds are diamonds, but they are black, and not transparent. Follow the link, below, to see photos of black diamonds.