|Europe||Fuentes de Ebro, Zaragoza, Spain||3 ¼" x 2 ¾" x 1 ½"|
Although describing these gypsum crystals (CaSO4 · 2H2O) with the word "gem" refers to their clarity, they would be a poor choice with which to make jewelry. Gypsum is the definition mineral for number 2 on the Mohs hardness scale - softer than your fingernail. A gypsum ring would be a nightmare to facet, and then it would not last long!
All that limits the sizes of crystals is space in which to grow and a supply of necessary chemical elements to keep adding to them. In the year 2000, miners digging a new tunnel in the Naica Mine in Chihuahua, Mexico, which produces silver, lead and zinc, drilled into a cave - the Cueva de los Cristales (Cave of Crystals). Within it were found gigantic gypsum crystals, up to 36 feet long and weighing up to 55 tons! They were formed over millennia around 1000 feet underground, at around 136° F. They formed in the cave from elements dissolved in the underwater brew that filled it. Exposure of the gypsum crystals requi res pumping over 13,000 gallons of water from the cave per minute - almost 19 million gallons every day.
A special door has been installed to isolate the cave from the mining operations. Even though the temperature in the pumped-out cave is 120° F and the humidity exceeds 90%, the crystals are nonetheless deteriorating slowly. Under these extreme conditions, exploration and scientific work go slowly - even with protective gear, a few tens of minutes is the limit for staying in the cave. After the mine becomes unprofitable, it is likely that the pumping will stop and the cave will fill with water once again. This will allow these remarkable crystals to continue growing.