From T. McGinnis's post on another website:

"What: Green Jasper
Agency: Ochoco National Forest
Tools: Rock hammers, picks and shovels only.
Note: Scarce, but beautiful. "

Directions from T. McGinnis:

"Directions: Follow US 26 past milepost 48 to Road 2630 (Pisgah Lookout road).
After 3/4 mile, merge onto Road 2210, turn right on Road 2210-300 for 2
miles, then right to diggings at end of the road. "

I tried to follow this on Google Maps, but it was hard without a distance given.  Starting from Prineville going east on US-26 past milepost 48, the road is National Forest Dev. 2630 .  It might be better to find it in person, so I will not post a GPS marker.