We will be visiting a pegmatite later in the term (badu hill). these were magma bodies that wd lots of water dissolved in the magma and this allowed the crystals to grow very large (up to 3 mil) - we'll see why later in the term. how much water do they have? let's figure it out. we took one cubic meter of a simple pegmatite that contained quartz (sio2), k-spar (kaisi. o.) and biotite (the annite end member: kfe; alsi3010(oh)2) and bashed it apart. we collected the bits and got about 45% quartz, 50% k-spar and 5% biotite (so this is a volume percent). a) how much (in kilograms) of each did we get? (hints: density of quartz = 2.65 g/cc; k-spar = 2.54 g/cc and annite = 3.1 g/ what is the weight percent of each of them? b) how many moles of each mineral are there in the 1 mº rock? how many moles of each atom: o, si, k, ai, fe and oh (treat as oh for now, don't break it apart) are there in the rock. also figure the mole percentage of each mineral (called a component) and mole percent of each atom (or oh). to figure mole percent, take the moles in the mineral (or atom) and divide by the total c) above we figured the moles present in the but this is not what was present in the magma chamber. pegmatites are often 10% water (by weight). as minerals crystalize, some of this water is used up (like in biotite) but most gets removed from the magma and moves off somewhere else as an ore or mineralizing fluid or brine. refigure your mole calculation above (part c) but this time include water (do not break it down, just compute as h20 - you can ignore the fact that the biotite used up some water, for now.) note, for part a above, we figured the weight of the minerals - we will now have to reduce those values by 10% each so that weight of qtz + kspar + biotite + h2o = 100%..