CompuServe Messages

>> 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. Thanks for that important missing data. I think I can look up the specific gravities of the metals involved, and work it out from this.