CompuServe Messages

Hi, Bill– Quartz and feldspars have specific gravities around 2.6-2.7, while the darker rock-forming minerals (more iron) tend to be above 3 – somewhere in between (say 2.8?) is my guess for the specific gravity of common igneous rocks. Limestone would be less dense, more like 2.3. "A cubic mile of backyard dirt" would be somewhere in this ballpark except that it includes a lot of air space. A cubic mile of solid rock, or a specific weight of dirt might be a more determinate starting point. All the percentages in EofB that I looked at were specified as weight percentages in the table headers; PPM readings may have also been by weight, and if found in a table specifying weight percentages I would assume as much. 10.7% H and 85.7% O is clearly by weight percent. Volume percentages would depend on what chemical combination was involved, thus I would be somewhat surprised to see it used in such a context. Atom counts could be used, but I would not expect them to be mixed with weight percentages unless this was made very clear. –Doug