Unicorn horns

[ladyramkin2000]

No: HPFGUIDX 90531

I may have just imagined it, as I can't find the reference, but I 
have a feeling that unicorn horns were used for something or other 
(potions, possibly).  Perhaps I'm confusing it with unicorn hairs 
being used in wands, together with things like dragon's heart-
strings. Do unicorns shed their horns or would there be any way of 
obtaining a horn without killing the creature, which would be 
unthinkable. I'm probably going off on a completely wild-goose chase 
here but it's worrying me a bit. Can anyone help?
Sylvia