Information on Mining Rubies

Formation

• Rubies are composed of aluminum oxide in the form of a mineral called corundum. Sometimes the corundum will contain a trace of chromic oxide, thanks to missing aluminum ions replaced by chromium ions. When corundum and chromic oxide are joined by a metal called vanadium, these elements can be heated and pressurized beneath the earth's surface to create the bright red crystal we call a ruby.

Geography

• Most rubies are mined in Asia, including Myanmar, Thailand and Sri Lanka. The Mogok district in northern Myanmar is the most plentiful source of rubies in the world, thanks to the rich alluvial deposits filled with limestone. Smaller ruby deposits have been found in India, Afghanistan, Vietnam, Australia, North Carolina and Montana.

Early Mining Techniques

• The Burmese in Myanmar were among the first to mine rubies. Because rubies are common in river valleys with rich alluvial deposits and limestone caves, they had to use three techniques: one for flat ground, one for hills and one for caves. The flat-ground technique involved digging small, square excavation pits ranging from two to nine feet in size. The sides of the pit were held up with bamboo while workers sifted through the underlying sand for rubies. To excavate on the side of a hill, workers dug trenches into the side of the hill. Bamboo pipes were used to route rainwater to the excavation site, powering away the surrounding dirt until workers could see the stones and extract them. Caves were the easiest---the ground material inside the cave could simply be turned, washed and searched for stones.

The Mining Process: Pit Method

• Today's pit mining is similar to the early Burmese mining method. Using either human labor or machines, large pits are dug. When the top layers of earth are carted away, the workers are left with either rocks or sand. These layers have to be carefully sorted (in the case of sand) or chipped away (in the case of rock) to reveal the gemstones. The pits can be filled in again or repurposed as landfills.

The Mining Process: Sluice Method

• A secondary method for mining rubies is sluicing, similar to the way miners panned for gold during the California gold rush in 1849. Gravel and dirt are hauled from the gem source and dumped into a long trough. Water is sent through the trough to wash the rocks and rinse away excess dirt. Workers must then comb through the remaining rocks, breaking them apart and inspecting them for rubies. Burmese tradition allows anyone who wishes, including women and children, to sit at the end of the sluice and paw through the rocks that get washed out, in case any gemstones were missed.