What's the difference between bone and plastic nuts?

Same job, very different material, and the difference is more noticeable than a lot of players expect — especially on acoustic guitars where the nut is doing real acoustic work, not just holding strings in place.

Density and tone transfer

Bone is dense and hard, which means it transfers string vibration efficiently rather than absorbing it. Plastic (usually a soft, cheap variety on lower-end guitars) is softer and less dense, and tends to dampen some of that vibration before it ever reaches the neck and body. The practical result: bone nuts are often associated with slightly brighter, more articulate open-string tone, particularly noticeable on unfretted or lightly fretted notes where the nut is doing more of the acoustic work.

Durability and wear

Bone holds a cleanly cut slot longer and resists wear from string vibration better than soft plastic, which can develop grooves and inconsistencies over time — one more slow contributor to tuning instability and string binding.

Tusq and synthetic alternatives

Worth mentioning separately, since "plastic" covers a wide range of quality. Materials like Tusq are engineered synthetics designed to mimic bone's density and tonal properties much more closely than a cheap injection-molded nut ever will.

Should you upgrade?

If your guitar came with a cheap, soft plastic nut and you're chasing a bit more clarity and sustain, a bone (or quality synthetic) nut is one of the more cost-effective upgrades available — small part, real difference, doesn't require touching the finish or the neck.