| Unless you use the open strings/harmonics alot it is kind of useless as far as material. But:
Brass: Allows for great sustain and clarity and last long too.
Micarta:An excellent synthetic bone substitute, tan in color; specified by Martin for nuts and saddles since the 1960s. Ivory in color and a bit softer than bone, it files and sands easily and gives a uniform tone. Another good choice for bridge transducer saddles.
Bone: Its hardness and density contributes to good tone, it polishes well, and it allows more precise slot filing.
Plastic: Just really cheap. material, better for saving lives than using for nuts.
Tusq: From Graph Tech. An advanced polymer material made with high levels of heat and pressure, to transfer string energy and sustain more consistently and efficiently. Popular with many guitarmakers for rich tone. Nuts are flat, except where noted
Grap Tech: As strings move across the surface of a Trem-Nut during bends and tremolo work, microscopic lubricants, more slippery than graphite, allow the strings to roll back into tune.
Slip-Stone Nuts: Our most "slippery" nut material. It's a new alternative for any guitar that's fitted with a traditional tremolo. Slip-Stone nuts are made of Delrin, a synthetic self-lubricating material that helps the strings return to pitch smoothly, without binding in the slots. Great for players who bend strings a lot.
I got this info from stewmac.com. As far as prices it ranges from material and size. Usually they are less than 10 bucks, they aren't too much though. Anyways next time you can do research on google or use the search function to find out.
Your welcome.
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"Don't B-flat, don't B-sharp just B-natural"
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