Antique Victorian Natural Gold Nugget 14K Gold Ring with Interesting Stone

Dating to the late 1890s or so may I offer this Antique Victorian ring. Featuring a 14K Yellow Gold shank & 22K Natural Gold nuggets, the center stone is rather unique. From a distance, the stone looks like a desert agate - you know, an agate with a sandy image - skyline image. But under a loupe, the shading on the side seems to be more "natural" matrix (like powdered sugar) yet the entire cab has been polished smooth - THERE IS NO ROUGHNESS to the touch. Which brings me to the FEEL of the stone - it's not HARD like a stone normally is but rather a little bit soft. Yes, this is hard to explain. Now when it came to making jewelry from natural gold nuggets during the heyday of the Gold Rush, there are only 4 things I can think of that were put into Gold Nugget rings (other than, or as well as, gold nuggets) - first, ore bearing quartz (which this definitely isn't;, second, natural stones (agates mostly); third, fossilized antler/cariboo horn picked up along the old miners trail; and fourth, petrified wood polished into a cab (from the area where the nuggets were panned). My guess is that the ring is either fossilized petrified wood or fossilized horn. Ring size is 7 on my sizer. Design on top measures 13/16" x 5/8". Weight is 7.6 grams. Just gorgeous!