You and the Smithsonian Institution may well be right. I'm just repeating what I recall hearing on the subject from a couple of Blackfoot grandmothers (neither was MY grandmother, but both were friends of my family) that ran an Indian gift shop outside of Glacier National Park back in the early 1970's.
Porcupine quill-work is a different thing than porcupine beadwork. Hairpipe beads were made of all of the materials you mention but they were also made out of porcupine quills. In fact, I think the reason they are called hairpipe beads is because they were first made from porcupine quills, and a quill is actually a specialized type of hair. The reason I think the beads this warrior wears could be porcupine quills is first, these beads look like other porcupine quill beads I've seen, and second, because of the reputation the porcupine has always held as an animal that is most dangerous when it is simply defending itself; that would be a message a native warrior would want to send to any foreigners invading his homeland...
The long “beads†used for the breastplate are called hairpipe. They can be made out of bone, horn or shell, among other things. I would guess that the beads on his breastplate are made of bone.
“Indians and animals know better how to live than white man; nobody can be in good health if he does not have all the time fresh air, sunshine, and good water.†-- Flying Hawk, Oglala Sioux Chief c 1930
