Hi Paul, it’s impossible to determine the origin of rough turquoise from a photograph. For example, the rough lots below are all from the Kingman Mine in Western AZ
Here’s a link to an article on the GIA website which discusses the challenges of field gemology. I think it will be of great interest to you.
What Country Do My Diamonds and Other Gemstones Come From?
You can also contact Joe Dan Lowry who is one of the foremost experts on turquoise. Lowry’s family have been involved in the turquoise trade for generations, he’s authored books on turquoise, given countless lectures and opened the Turquoise Museum located in Albuquerque, New Mexico.
jacob@turquoisemuseum.com
info@turquoisemuseum.com
Cheers and best of luck with your research