<p>It’s a small piece of obsidian, just over 5 centimeters long, likely found on a hard-scrabble piece of ranchland in the Texas panhandle. But when SMU anthropologist Matthew Boulanger looks at it, he gets a mental image of Spanish explorer Francisco Vasquez de Coronado making his way across the plains more than 470 years ago in search of a fabled city of gold.</p>