As best as I can figure out, there is a real type of agate called Jumping Jeep Moss Agate. If anyone can chime in on this, feel free. The “Shirts” in the story refers to Shirts Quant, who was a real person.
Here’s the story I found . . . “ANOTHER FAMOUS DISCOVERY IS THE JUMPIN JEEP MOSS AGATE FIND NEAR MITCHELL OREGON. NOW SHIRTS AND A FELLA BY THE NAME OF MITCHELL LOCATED THIS CLAIM WAY UP ON THE SIDE OF A MOUNTAIN. THEY WERE GETTING SOME FANTASTIC AGATE OUT. THERE WAS A HUGE BOULDER OF SOLID MOSS AGATE WITH REDS AND GOLDS, BUT THEY COULD NOT BUDGE IT. THEY GOT THE IDEA OF BRINGING UP AN OLE WILLYS JEEP AND IT HAD A WINCH ON THE FRONT END, MAN THEY WINCHED THAT HOSS UP AND HIKED TO THE JEEP AND GRINNING THEY TURNED ON THE WINCH AND THE ROCK BUDGED A BIT AND BEFORE THEY COULD STOP IT THE JEEP TOOK OFF ROLLING DOWN THE MOUNTAIN WITH THE ROCK!!! IN THEIR HASTE THEY HAD FORGOT TO ANCHOR THE JEEP. SHIRTS SAID THEY JUST STOOD THERE IN AWE HE LAUGHED AND SAID “A COUPLE TIMES THAT JEEP WENT WAAAAY UP AIRBORNE” HE SAID FOLKS FROM ALL OVER HAD TO COME AND LOOK AT THAT JEEP…”
http://stores.ebay.com/RHODES-CABBIN-AND-GEMS/THE-PROSPECTORS-PAGE.html
Here’s one picture of Jumping Jeep Plume Agate: