A Scientific Study of the Absorption of Evil by Vivianite

摘要

Every mineral collector has at one time or another probably drooled over a gemmy green vi vianite from Morococala, Huanuni, Llallagua or Tomokoni in Bolivia, or Trepca in Serbia, or the Blackbird mines in Idaho, but hesitated to buy it because they had heard that vivianite crystals are unstable and will eventually turn black and fall apart, especially when exposed to bright light; or perhaps they went ahead and purchased a fine crystal anyway because some reputable high-end dealer (undoubtedly a highly successful used car salesman in a previous life) assured them that this particular extremely fine and important specimen came from a locality which produces stable vivianite - stable because of some magical ingredient in the matrix, or absence of something in the matrix, or lack of oxygen at the high elevations the crystal grew in, or lack of bacteria at the high elevation You get the picture. Or perhaps the dealer convinced the customer that he wouldn't have a problem with vivianites because he lived in a sufficiently dry region (or a sufficiently humid one), or at a high Rocky Mountain altitude with low atmospheric oxygen.... All of this nonsense comes from statements I personally heard while wandering around mineral shows, or read in dealer advertizing; I promise I didn't make any of them up. Unfortunately, the bad news is that ALL vivianite suffers from the same type of instability; the good news is that its decomposition can be easily prevented. But before we discuss how to preserve vivianite specimens we need to understand the chemical mechanism involved in its self-destruction.