OK, to actually give you an answer, I need to ask a few questions of my own. (1) You're talking about an "amulet". Are you talking about a medicine bag, a beaded necklace containing a beaded medallion, or a whimsy-type beaded and stuffed item that isn't worn? (2) What tribe? I actually think the second question is the most important since you're bundling "Native American" into a large basket when each tribe was a completely separate culture with different beliefs, governmental structures, and beadwork colors and patterns. If you think of Europe in the Middle Ages with the 100 kingdoms of Germany added to those of France, Brittany, Spain, Portugal, etc., you might have a better idea of the geography of politics existing within the Native American communities.
As a beader of 50 years and a retailer of beads and supplies for the Native American population in my larger area, I possibly can help you, but information will allow a more tailored and accurate response on my part.