GeologyRocksThe differences between a magmatic, a metamorphic and a sedimentary rock?
- Login to post a new forum topic.
Rank:
Contact:
basically, it's not
Mon, 07/02/2007 - 09:38basically, it's not easy.
magmatic, metamorphic and sedimentary refers to the forming of the rock, but the forming is not easy to identify from the apperance. there are some clues: if it has crystals in the stone, it's probably magmatic. if it's stratified, it can be sedimentary or matamorphic. but that is not always the case.
you can identify if you know some type of them. Like granite, gneiss, shale, marble.
Rank:
Roles:
Contact:
bram wrote: Hello
Mon, 07/02/2007 - 12:38Hello everybody,
I’ve got a question: What are the differences between a magmatic (or pluton), a metamorphic and a sedimentary rock? I mean the differences you can see just by looking at the rock (without using a microscope or something like that). I have already searched the Internet, but I couldn’t find anything clear. I hope you can help out.
Greetings Bram.
The usual way is experience! To generalise a little:
Igneous and metamorphic rocks are crystalline - they are composed of interlocking crystals. Hopefully, these will be visible without a microscope (but probably needing a handlens). Sedimentary rocks are composed of rock fragments and as such are suaully composed of discrete grains.
Some things complicate this. Limestones can have a very interlocking "look" to them. Volcanic tuffs can have a very "bedded" look to them and look very sedimentary. Some volcanic rocks look very much like sedimentary features! Sandstones can have silicate cement, locking together the discrete grains - again giving the rock a "crystalline" look to it. Of course, metamorphic rocks have a grade, depending on the amount of heat and pressure they have undergone. Starting from a sandstone and heating a bit results in a quartzite - not that different to be honest!
Hope that helps and has not confused you too much 
Rank:
Contact:
The differences between a magmatic, a metamorphic and a sedimentary rock?
Submitted by bram on Mon, 07/02/2007 - 06:40.Hello everybody,
I’ve got a question: What are the differences between a magmatic (or pluton), a metamorphic and a sedimentary rock? I mean the differences you can see just by looking at the rock (without using a microscope or something like that). I have already searched the Internet, but I couldn’t find anything clear. I hope you can help out.
Greetings Bram.