This mineral was on the list of critical commodities during the First World War. Peaceful uses have been found eventually, now the stone being part of any large celebration.
Celestine, also known as celestite, derives its name from 'caelestis', a Latin word meaning celestial. The mineral is named for its delicate blue colour, but as it turned out, white, pale green, reddish, and even colourless variants occur.
Celestine crystals can reach enormous sizes. In 1897, Gustav Heineman – an owner of a winery in Ohio, US – discovered a 10 m deep cave whilst digging a well. The cave walls were covered with massive crystals identified as celestine, and Mr Heineman decided to start mining. However, this business did not succeed, so he turned the property into a tourist attraction. The Heineman winery survived Prohibition when alcoholic beverages had been banned for sale primarily because of tourist revenues. Since 2016, the cave has been open for tourism, with guided tours arranged to see one of the world's largest celestine vugs, where crystals grow up to 0.5 m in length and above.
Before Mr Heineman had stopped the mining, he would sell much of the celestine to fireworks manufacturers who valued it as a pyrotechnic colourant. Celestine causes a flame to burn with a red colour. This came in handy throughout the war years, as the mineral was used for making signal flares. Launching flares was crucial for communicating one's position, indicating the direction, and signalling to retreat or attack. World War I ended over a hundred years ago, but celestine is still used to manufacture red fireworks.
Celestine is one of the principal sources of the element strontium, hence its use in the food industry in the 19th century. The mineral helped separate sugar from syrup whilst processing sugar beets until calcium replaced it. This metal was considered a cheaper and, more importantly, safer alternative. Many believe that strontium is radioactive, which is not true – only the isotope strontium-90 is hazardous to health, and celestine does not consist it.
Strontium does not occur naturally in its pure form and is mainly mined from minerals, celestine being one of them. It has various applications in nuclear energy; other uses include the production of paints, rubber, electric batteries, ceramics, X-ray shielding glass.
Celestine is of interest to collectors across the world. It is a rare mineral, fragile, with low hardness. The most valuable specimens are pale blue crystals found in Madagascar, translucent variants from Austria and gemstone-quality samples from Spain.
If exposed to direct sunlight, celestine can lose its colour. The mineral is also notable for being able to fluoresce in UV light. An explanation is that the stone sometimes contains calcium or barium.
