As we all know, most rocks are composed of multi kinds of minerals, take granite for example, it is composed of quartz, feldspar and mica, however, there are also rocks composed of a single mineral, for example, calcite (CaCO3). I wanna know if there exists any other kinds of rocks composed by a single kind of mineral?
Of course, there're a lot of them: pyroxenite, quartzite, dunite (over 90% olivine), anorthosite (over 90% plagioclase feldspar), marble, chalk, gypsum (although it is a mineral, it can be found occupying large areas) , anhydrite (the same as gypsum, it's a mineral), amphibolite...etc
Dear Mr. Ma Zhaoyang,
the technical term "monomineralic" is of common use in petrography be it genetically or used in terms of application. It is only important to note where you draw in your classification the boundary between major and minor or accessory minerals. There are many classification schemes which set the line at < 10% but it depends on your aim in your studies. Even this percentage value may stand at too high a level if you have to deal with contaminants or impurities.
Best regards
H.G.Dill
Dear Harald
Thanks for your advise. I wanna model the mechanical properties of rocks using molecular dynamics simulation, however, because the heterogeneity of rocks (because most rocks are composed of various minerals), I choose to simulate the monomineralic rock first, therefore, I can ignore the heterogeneity problem.
Many thanks
Regards
Dear Mr. Ma Zhaoyang,
if you are going to model the mechanical properties of monomineralic rocks, its important to consider the size and the shape of the grains and how are the boundaries between them. Marble, for example, has diferent mechanical responses depending on whether the grains are poligonal or not. You can have a look at this paper.
Article Grain properties, grain-boundary interactions and their effe...
Best regards
M. Durán
Anorthosite, by definition must have more than 90 % of Ca rich-plagioclase, such as labradorite, bytownite or Anorthite
Another one is carbonatite more than 90% calcite.
Molecular dynamics simulation is likely to be indicative of macroscopic mechanical properties in single crystals (individual crystals made of a single mineral), but not necessarily in multi-crystal monomineralic rocks.
Think for example about solid gypsum rock made of interlocking large gypsum crystals (e.g. evaporite rock of Messinian age in the Mediterranean Area, Photo 1), and another gypsum rock made of very small granules of gypsum deposited in thin layers as "turbidite" (e.g. Photo 2).
Photo 1 = http://users.uoa.gr/~vkarak/photogallery/(1)Messinian%20gypsum%20(selenite).JPG
Photo 2 = http://users.uoa.gr/~vkarak/photogallery/(6)%20Gypsum%20turbidite%20(Cu=%20cumulate,%20Ar=%20arenite).JPG
Both examples are taken from http://users.uoa.gr/~vkarak/preapulian.html.
The two rocks are both made of nearly 100% gypsum (CaSO4.2H2O, Calcium Sulphate Dihydrate), but their mechanical properties are quite different!
Dear Prof Roberto
Thanks for your suggestions. I am currently thinking about simulating the rocks that composed of multi-minerals, taking granite for example (composed of feldspar, quartz, mica), any suggestions?
Regards
Most of the recent molecular dynamics simulation work done to model mechanical properties of solids concentrated on mono-crystalline objects or on very small objects such as nanotubes.
Only a few works to date dealt with polycrystalline rock material, and one of such works is:
http://www.ipme.ru/e-journals/MPM/no_1301/krivtsov/krivtsov.pdf
I would suggest to start simple, and adding complications only in case of success with the previous stage of complexity.
You could start modelling individual macroscopic crystals of the main granite forming minerals, and compare your results with actual mechanical tests performed on the selected real mineral crystals.
In case of success, you could try modelling simple aggregations of crystals assuming no porosity, and simplified crystal boundaries (maybe taking inspiration from an actual granite thin section), and mechanically test the equivalent real pieces of solid rock.
In case of success, you could add further complications (fractures, intergranular porosity, minerals due to weathering, etc.).
Dear Roberto
Thanks for your kind advise, which is very helpful for my further study and research.
Have a great day!
Best regards
Zhaoyang
Yes, there are many rocks made up of single mineral (monomineralic). I agree with the answers of Dr. Duran and Dr. Dill.
hello
of course there is monomineralic
travertine , limestone, anhydrite, chert, etc