I know nothing of gems and minerals, as I'm strictly a metal detector enthusiast . But I've heard of some people who get pieces good enough down there to market and sell . Nothing astounding or abundant money-wise (lest it be inviting to commercial exploitation), but enough that a hobbyist can make it worth his buy/sell time.
I used to detect with a guy in Monterey about 10 yrs. ago. He was an amateur jeweler. He was collecting the stuff, putting it in jewelry, and selling it on ebay. Was making enough to support a modest living doing it. Not sure if it was jade he was getting from down there, or something else.