> around the land, almost half a mile long ... past the Allegheny Mound Ant cities ... up the volcano, over the 250-million-year-old gabbro ... through three different New England habitats ... if you're coming to the party, bring a bike and a helmet. I shovel gabbro (known as "rotten rock" locally) to make deep, weed-free paths around flower beds. The Vietnam Memorial in Washington is gabbro. "Gabbro often contains valuable amounts of chromium, nickel, cobalt, gold, silver, platinum, and copper sulfides." Our gabbro contains a few plastic cowboys. Gabbro was named by a German geologist for a town in Tuscany.