I am unsure about what you mean by "suruca"? Isn't that a place in Brazil? lol! I have found gold here by "mossing", if that is similar! As far as foxtail, the area I live in does not have much foxtail, that is mostly in eastern Montana and in the northern parts on the plains. I have found gold in tree and plant roots, but no diamonds or sapphires. I would say 99% of the sapphires I have found are way too deep to be near any root systems, and really most I find are in creek beds under the water behind large boulders. One lady a few years back was jogging on a gravel road north of Great Falls Montana, and she found a 14 carat diamond on the gravel road! I however have not found any diamonds. I know they are here, but they are pretty rare to find. So, is "suruca" like when you use a sieve? I mostly will use a sluice box, then I'll use a sieve on the material from the sluice, then I pan it, that way I get sapphires AND the gold, both big and fine. Sometimes I'll re-pan my tailings too! I find all kinds of stuff, garnet, sapphire, unknown crystals, agate, even hemetite fossils! One of these times soon, I'll get some material and take a pic after I pan it to show you all the interesting stuff left in the pan! One thing I have not found, but hope to soon is platinum. There are a few creeks by Phillipsburg Mt that are supposed to have some fine platinum!