The rock that is known as Mushroom Rhyolite or Mushroom Jasper is found in several areas northwest of Phoenix, Arizona. The rock gets its name from the repeating gray pattern that sometimes looks like a mass of growing mushrooms. The formation is an atypical thunderegg formation where most of the thundereggs did not completely form. The thunderegg started to form, stopped and started again forming the gray overlapping shapes in the rhyolite. In certain areas a reddish halo surrounds the outside of the gray massive thundereggs providing a colorful contrast on the rock. Outside the reddish halo the host rock can be a greenish color and when it is hard enough provides a gray, red and green color combination that is very attractive.
This deposit of Mushroom Rhyolite was explored and developed by my friend Jake He dug the area by hand for several years and posted a claim on it called the Sherrie Ann. He had planned to mine it with machinery but the operation on his brain tumor in October 2010 put an end to that. He asked me if I wanted to buy the claim from him and I did.
The story of dealing with the BLM to get approval for my ½ acre of mining activity is too long to present here. Let me just record here that the amount of taxpayer money spent on the approval will far exceed the total mining costs of the mining operation. I had planned on starting in the spring of 2011 but was unable to get approval until late October 2011.
I rented a 320 Excavator from Caterpillar for one week and had it moved close to the claim on November 2nd. Jose Luis, my partner in the Mexican company, Agata Exploraciones SA de CV, was with me to experience the operation. Dale Ott, who dug here with Jake, was there to give us advice and encouragement. Dale has a mine property about 30 miles away and offered a place to store rock that was extracted.
The deposit is composed of perlite and rhyolite layers exposed on end up a gentle east slope of a north south ridge. The rhyolite layers contain massive clumps and sausage shaped groups, as well as individual thundereggs of all sizes. Many of these layers have been dug by hand and it was easy to see where they were in the ground.
The claim is about 1 ½ miles south of road so it did not take too long to drive the excavator to the mine site after the truck dropped it off. I had arrived the day before with my trailer and set up a small camp so we were ready to start soon after I drove the machine to the mine.
We started digging on the southern end of the claim on one of the lower layer of the exposed rhyolite. This area had been dug by hand earlier, and according to Dale had produced some of the best reds. It wasn't long before we were creating piles of rock to haul back up to camp. For the next couple of days I followed the rhyolite between the layers of black perlite and then moved the excavator up the hill to the next exposed layer of rhyolite. Dale told us the green was a little thicker and better on the top of the ridge so I worked the top of the ridge towards the end of the week. One disappointing aspect of this exploratory mining operation was the depth I was able to dig with the excavator. The rock is so dense and solid that I could not dig more than 2.5 feet into the surface with the excavator. To get material deeper it will be necessary to rent a hydraulic ram or use explosives. The massive thundereggs are fairly dense in their individual layers and we were able to produce over 5 tons of rock in one week. We hauled some of the rock to Dale's place, put the rest in my truck and Jose Luis's trailer and left for Tucson.