Is is quartzite or is it sandstone? How should I know? Do I look like a geologist to you? What I do know is that it makes for some great bouldering.
La Barrosa is the small sierra just outside of Balcarce, and like all the sierras nearby (e.g. La Vigilancia, Difuntos, Sierra de los Padres) the potential for bouldering and short routes (up to about 15 meters long) is excellent. Until recently, this place was basically the personal and exclusive playground of me and my wife. But now it seems to be catching on a bit and there are more and harder boulders being put up all the time. There is still a lot of new bouldering potential, but be prepared to hike around and scrub lichens off rocks. The route potential is more limited, but in 2005 I put up some more, and even harder bolted lines.
Right now there are about 35 established routes (some which require gear placements) from 5.9 to 5.12, as well as some 250 boulder problems from V0 to V11. There doesn't seem to be any access problems on the front side (when accessing from the city of Balcarce) but EXTREME CARE should be used when accessing from the private property on the backside. PLEASE do not disturb or cut fences, do not make fires and do not leave trash. And be DISCREET. Anyways, most of the areas on the backside are difficult to find without a guide. Feel free to get a hold of me any time for information