Re: What type of stone is this? Is this piece Native America
I'm no gemologist, but that stone looks like it could be a Jasper or Agate. It might be attempting to imitate Turquoise, the stone which Native Americans would use, but the colour (too dark) and patterning (heavy brown content) doesn't look very similar.
I have read that Native American jewelers do not stamp 0925 or .925 on their silverware (meaning Sterling Silver with 92.5% silver content). They would more likely just stamp the word "sterling".
And, of course, if this was supposed to be an older piece (pre 1930s) there would be nothing like 925 or Sterling stamped on Native American jewelry.
Re: What type of stone is this? Is this piece Native America
The stone reminds me of chryssocola beads I used to own. Unfortunately that guess won't help identify the necklace since chryssocola is pretty widespread. Some of the necklace design elements - like the small stations - do look similar to Native American Jewelry I've seen. Others, such as the rope-like edging, not so much. Anyhow if there are no halmarks at all I think you can rule out Mexican origins. Asia is a possibility though, particularly Indonesia, India, and Sri Lanka.
I'm sure there are forums focused on Native American jewelry that can help you with that possibility.
Good luck!
Eta I just noticed that it is stamped 925 and sterling. Mexico, pre 1948, is a possibility then.