I want something different for my rock collection, Alice thought, scrutinizing gravel in furrows at her toes. Where she meandered, pebbles lay scattered over the field. Her feet froze. She gasped. She stared at a stone, then snatched it up. Squeezing her fingers around her treasure, Alice put wings to her feet. Nearing the house, she spied her brother on the porch. “Daniel! Look what I found!”
He turned her glittering stone over in his hand. “What is this?”
Alice fairly bounced. “Is it gold?”
“Let’s ask Mom.”
Mom examined the pebble and smiled. “It’s pretty, isn’t it? Years ago I found one like it. It’s not real gold; it’s pyrite. Some people call it ‘fool’s gold.’”
“Why is it called fool’s gold?” Daniel asked.
“It looks like gold, but it does not have value like gold does. If you put gold on a hot stove it won’t be damaged. If pyrite is heated, it smells bad, smokes, and sizzles. Some native Americans used pyrite to start fires.
“I won’t!” Alice declared, “I’ll keep it in my collection.”
Fire won’t hurt gold. Daniel thought, becoming curious. We talk about something being pure as gold. How, exactly, is gold mined and refined? He began to research.
Gold artifacts found in Bulgaria may be some of the oldest discovered. The world’s oldest known gold mine may be the Sakdrisi site in the country of Georgia. Rock carvings in Egypt, from as early as 2500 B.C., show washing of gold sands and use of a small furnace for melting the precious metal. In the Egyptian desert, old gold mines have been found.
Daniel learned that mining gold is hard work. Gold in streams is called placer gold. Panning is one method of placer mining. Miners pour sand and gravel containing “color” (gold) into wide shallow pans. The pan is held under water and shaken. Gold, denser than rock, settles to the bottom.
Miners also build sluices, which are long inclined troughs, with riffles for catching gold as water and placer material flow through.
Some miners dredge for gold, using suction tubes or excavators to feed a screening plant and sluice box.
A cradle, called a rocker box, is a high-walled box with riffles for trapping gold, in a manner similar to sluicing. Rocking the box gives the movement of water required for gravity separation of gold from “pay” gravel.
Most of the world’s gold comes from extracting gold enclosed in rock, called hard rock mining. Underground mining extracts ore through shafts or tunnels. Open-pit mining is another method.
Daniel discovered that refining gold is dangerous work due to toxicity of substances used. Gold ore contains impurities. Refining separates valuable metal from dross. Finely ground ore is mixed with sodium cyanide; then gold cyanide is separated from the ground rock. Zinc is added to bring out the gold. Sulfuric acid removes the zinc. The gold sludge left is smelted into an ingot, a mass molded into a shape suitable for shipping to a refinery for final purifying.
Pure gold melts at 1948° F. At 5173° F it boils.
Gold is ductile—it can be drawn out into fine wire. It is malleable—it can be hammered into thin sheets. It does not tarnish—it is resistant to rust and other chemical changes from the air. Daniel thought, That’s where we get the expression “Good as gold.”
Daniel took a break to eat a snack. Alice watched him spread golden honey over peanut butter on a slice of bread. “See, Alice,” he said, “Honey is clear gold in color, and it won’t spoil. It’s good as gold.”
“No fool’s gold either,” added Alice.
