From "Sherlock: The Empty Hearse (#3.1)"
[analyzing a hat
] This is a chullo, the classic headgear of the Andes. It's made of Alpaca.
Icelandic sheep wool. Similar, but very distinctive if you know what you're looking for. I've written a blog on the varying tensile strengths of different natural fibers.
I'm sure there's a crying need for that.