Because what seems a simple stalactite here is not made by calcium carbonate, but is made by opal, and one of those stalactites can require tens of millions of years to be formed.
因为这样一个看起来普通的钟乳石， 不是是由碳酸钙组成的， 而是蛋白石， 而一个这样的钟乳石 需要上千万年的时间才能形成。