Obsidian originated from a geological formation known as the Trans-Mexican Volcanic Belt, spanning 621 miles (1,000 kilometers) from the west to east coasts in central Mexico, the study authors noted.

As of April 10, get the Google Nest Learning Thermostat for $239.99 at Amazon, down from its usual price of $279.99. That's a discount of $40, or 15%. Currently, this price applies to the Polished ...