 | "What we would like to know, Lou, is whether a rock's mineral composition can tell us if it is metamorphic!" |
|
 | "Yes, that's what we're talking about!!" |
|
| "How would you suggest we go about answering that question, LOU?!" | |
|
| "What would be most straightforward (and therefore probably not the right answer we want in the devious universe you geologists inhabit) would be to examine lots of metamorphic rocks and see how what they are made of compares to what igneous and sedimentary rocks are made of!" |
|
| "Why do you say 'you geologists', Lou! I was hoping you'd say 'we geologists'! (Sigh!)" "But you're right! We're back to that circular conundrum! We'd like to know if a rock is metamorphic by the minerals it contains, so we should go look at metamorphic rocks to see what they contain! But how do we know whether the rocks we go look at are metamorphic!!" |
|
| "This time I've got an answer! There must be some other sure-fire way, aside from its mineralogy, of telling whether a rock is metamorphic! Then we could see whether such rocks have anything unique about them mineralogically!" |
|
| "That's something to think about!" "I've got two comments to make!" - "'Metamorphic' means a rock has changed! It changed because is was heated up and/or squeezed! And maybe it's also had its chemical composition altered! So we need to look for signs that one or more of these things have happened to the rock!"
- "The starting mineralogy of the rock that undergoes these changes could be anything found in igneous, sedimentary, or older metamorphic rocks!"
|
|
| "Sounds good to me! So we need to see where in nature rocks have been indubitably cooked, squeezed or both!!" |
|
| "We'll do that when we consider "Rock Structure' and 'Field Relationships'! In the meantime, I'm going to cheat and tell you the names of the minerals found in some typical metamorphic rocks!" | |
|
| COMPARISON OF MINERALS FOUND IN METAMORPHIC AND IGNEOUS ROCKS |
| Minerals found
in metamorphic rocks
but not in igneous rocks: | Minerals found in metamorphic rocks and found in igneous rocks: |
| CALCITE | AMPHIBOLE |
| GARNET | BIOTITE |
| SILLIMANITE | FELDSPARS |
| STAUROLITE | MUSCOVITE |
| TALC | QUARTZ |
|
"Now go visit the Metamorphic Mineral Assemblages Rollover!! I want you to see what some metamorphic rocks look like and the minerals they contain! (You don't have to remember any of their names!)  | |
|
 Here are questions that will help you decide if the mineralogy of a rock can provide clues as to whether it is metamorphic in origin.
|
| To check your answers and get additional hints and information, click on the link. |