A former basalt quarry left behind this deep pit with steep sides, which filled with water due to rain. Initially, the resulting lake was called Lacul Brazi (Fir Lake), but its intense green-blue color soon led to its now familiar name: Emerald Lake (Lacul de Smarald). The finely pulverized mineral rocks left behind by basalt mining predominantly reflect the blue-green spectrum of sunlight. Emerald Lake is a celestial pond, the name given to lakes filled exclusively by rain from clouds.