There's an awful lot to know before you can make a totally firm judgment on where your turquoise comes from, if you're only going by pictures and not handling in person and a professional dealer hasn't guaranteed its origins. For example, some mines yield both blue and green stones. Some originally blue turquoise can now look green, from change over time. You also have to have a good understanding of matrix (the host rock that you see mixed in with the turquoise). The color and pattern of matrix are important indicators of the origin. In addition, you need to know a bit about the mining side of it: several of the legendary American turquoise mines have long been exhausted, so you won't see the material from them too often. Some mines have been opened much more recently--a 1970s pendant, for example, can't have a stone that could be mined only from 1990 onward. And so on.
Then, finally, there's the huge influx of Chinese turquoise, especially spiderweb, which is pretty and can be high grade (depending), but most of it is lower grade that just looks like the expensive American stuff.
Complicated!
It's what you see in old pics of Navajos too, as you've posted--the vintage photos show a great jumble. I have limits on doing that because I can't tolerate too much weight on the neck...wonder how Ms. Iris manages that!