I had to email a customer and tell him that I just couldn't bully my way out to the shop and look for his rocks. Yesterday I tried again and the walk was too slippery. I have had an irrational fear of falling ever since a concrete step crumbled under me, which has been a few years ago. Today it said -35 so I am delaying that cold trek again......Apatite is a very common phosphate used for fertilizer. It is a source of fluoride. Deposits are derived from fossil bone. Monazite contains uranium and other important raw materials so is mined commercially. It is used in isotope analysis to determine the age of rocks. Vivianite and erythrite are secondary phosphates. The latter is reddish and vivianite is colorless, blue or green. Variscite is a beautiful material, sometimes used for carving or jewelry. It is a hydrous aluminum-iron phsphate, white to greenish in color.