There used to be some nice carnelian and plume agate outside Lebanon, but it was all on private land. I don't know of anything accessible in that vicinity today. You can still find some carnelian in Ames Creek south of Sweet Home (take 18th st. south for a couple miles before checking out the creek bed). Petrified wood in there too, but as you are going to Holleywood Ranch, you'll already have some pieces not tumble-smoothed in the creek. Going up Quartzville rd. at Green Peter reservoir (just east of Sweet Home) may also interest you. You have to travel quite a ways up the road (until you are clear of the reservoir) before you are in an area with better rockhounding possibilities. Aside from panning for flour gold in the creek (and lots of folks are usually there doing that), take a look at through the big piles of spoils here and there on the west side of the road. I once found a palm-size nodule of native silver crystals looking through one of those. Probably some snakes in there, too, so keep an eye out. There's a bridge over Quartzville Cr. about a mile before/below where Boulder Cr. joins it, and if you cross over, there are some pyritohedrons floaters in a roadcut a short ways up the hill (look for a whitish tuff stained with red on the left side of the road). The crumbly white tuff is supposed to be toxic, so wash your hands afterward. As you go further up the creek beyond the day-use picnic area, be aware of claim markers, as there are some gold claims up there. Should be some agate, too, but I'm not sure if there are any specific deposits. Many of the side roads go up from the creek onto private timberlands, and more often than not they don't take kindly to folks wandering around their property (plus a head-on with a log truck isn't going to be pleasant going around a bend in a narrow dirt track). That area is a nice, mostly shady and cool place to spend on a hot day with your feet in clear water looking for rocks, though.
