Looking for solitude, beauty and maybe a few thrills, my buddies and I were hoofing it in the high country of California’s eastern Sierra when the mountains served up an unexpected treat, as they always do. Beneath us, at about 10,500 feet, was a lake like none I’d seen. It glistened with such an intense, cinematic glow that I would venture to call it the bluest lake in the Sierra Nevada. … [T]he spectacle was Burro Lake in the Hoover Wilderness. … Greg [Stock, Sierra Nevada geologist] says glacial flour is probably helping create the lake’s bright blue color. But the real secret, he suspects, is the presence of a common but surprising chalky compound in the water: calcium carbonate, the main component of limestone and marble. It appears to be flowing into the lake from a creek and other runoff in the basin.