The flight instructor reported that high altitude pinnacle landings were being conducted with the pilot receiving instruction. He reported that the approach was made to a pinnacle landing site with an elevation of "roughly 8000 feet" mean sea level (MSL). The flight instructor reported that "as we got closer to the ground and to the spot (around 5-6ft above the ground with a descent rate of around 100ft/min) the rotor rpm began to droop and we started to descend." He reported that he tried to increase airspeed and go-around and that, "this made us descend further and the gradient of the down sloping terrain was not sufficient for us to avoid ground contact." The helicopter skidded forward on the ground, the right skid caught terrain, and the helicopter rolled over on its left side. The helicopter sustained substantial damage to the fuselage and to the tail boom. The density altitude for the accident area was calculated and exceeded the in ground effect ceiling and out of ground effect ceiling values provided by the flight instructor for the accident area. The flight instructor verified that there were no pre-impact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation. ADDITIONAL INFORMATION The altitude for the latitude and longitude coordinates provided for the high altitude pinnacle landing site was determined to be 8269 feet MSL, at the top of a volcano.