"There were some proponents of a bigger dairy industry in Laos to improve a calcium deficiency," says Durst, whose favourite is Fried wasp - "very crispy and a nice light snack".
Under UV light, clean sand appears purple or black. Some minerals, such as calcium carbonate in seashells, glow blue, as does a shovel handle in the picture above.
They would leave subtle clues in the isotopic composition of the limestone by shifting the ratios of light to heavy carbon and oxygen atoms in its calcium carbonate.