In a 2007 photo, scores of monks, jaws set, walk through the streets of Yangon, Myanmar. The label says that, a few moments later, the military government would open fire on the peaceful protest in Burma’s largest city. But what Christian Holst’s camera captures is the scene’s nearly palpable silence. A photo exhibit purportedly about rubies, the Field Museum’s “BLOOD/STONES: Burmese Rubies,” works more as a primer on Myanmar’s 50-year history under totalitarian governments that seize control by selling off the country’s resources (most notably, rubies). The deviation from the titular subject matter suits us fine: In the day of the 24-hour news cycle, it’s refreshing to find a vetted historical resource that moves past immediacy and shock value.