ALS in Reno, Skyline in Tucson are both good. Some labs, like Skyline, have a $300 minimum order. And there is shipping to think of. Are you sure you want to waste your money on analysis of desert gravel - TWDL is a scam, no doubt. I can tell you what you will find - nondetect gold and platinum, background levels of silver, rare earths.
Also, how are you going to sample - how big is your sample, how will you fairly divide into 2 or 3 samples to send to different labs, and are you prepared to pay a couple hundred bucks each plus shipping? One sample is insufficient to evaluate a prospect, but again, TWDL is a scam, and their claims are nothing but worthless desert dirt.