Rocks and Minerals
Rocks and minerals are very interesting. But you may wonder, what is a rock, how are they formed, how many different minerals are there? Well you'll have to look at all these pages to find them out. Did you know that minerals are found everywhere? You could be wearing a diamond ring, and that's a mineral, everyday you use minerals. They could be found in your cellphone, car, coffee pot, and even the computer you're on right now!
Minerals
Minerals are everywhere, now you might wonder, "What is a mineral anyways?" Well a mineral is what makes up a rock, for example diamonds could be found in any ordinary rock, and gold is found in rocks also. Identifying the crystal is one of the most important physical classifications of a mineral. There are six major crystal systems: Cubic, Tetragonal, Hexagonal, Orthorhombic, Monoclinic, and Triclinic. The Grey picture below will show you the shapes. But more often than not the crystal is too small, so the naked human eye could not see it. Another important property to the physical value is the hardness of the mineral.
Another important property to the physical value is the hardness of the mineral. Hardness is tested to see how long the mineral could resist to being scratched. Now how can minerals be classified for their hardness, well German scientist Friedrich Mohs wondered the same thing in 1812. He created a scale of 10 minerals with a significance of hardness from a scale of 1-10. The higher the mineral is on this scale, the harder it is. Your fingernail could scratch up to the number 2 on the list because your fingernail's hardness is measured are 2.5. Copper is the same, though it can only scratch up to fluorite (3) as it is rated at 3.5. The picture down below will show you the Mohs Scale of Hardness,
Lustre is another way to classify minerals. But it is there to determine the mineral through the shine of it. The Lustre of the minerals is identified on how it reflects off light. If the mineral is shiny like it's just been polished, it would be said to have a "metallic structure". And vice-versa, if the mineral doesn’t shine, it is called a non-metallic structure. Now there are different names for Lustre. There is "Adamantine" which has a nice, very bright shine to it. Second, "Glassy" which is pretty self-explanatory as the mineral looks like a piece of glass. Then is Greasy, again pretty self-explanatory, it looks like there is oil on it. Next comes Waxy, which looks like wax is on the mineral. Then Pearly, which shines like a pearl. And lastly, silky which shines like there is a layer of silk on it.
Color is one of the most important features on a rock, for example some women like to wear Emerald, Sapphire, Amythist, Ruby as jewelry. Though color is one of the least important ways to classify a rock, but if scientists couldnt tell them apart they would use color to classify the mineral. I say this because some Granite rocks have different colors and some minerals that have different names. For example, When Corundum cantains Aluminium and Oxygen, it is pearl white. When it has Iron and/or Titaniumin it, its blue and called a Sapphire. Or when it contains Chormium it is red and called a Ruby.
When a mineral with a hardness of less than 7 in rubbed on a piece of unglazed porcelain tile it leaves a streak. The streak is what the color of the mineral is in powder. Its the same as if you rub white chalk against a blackboard or the sidewalk, it would rub of the color white. Another example would be if you rub an Emrald on the tile, it would be a greyish-green. If you put Diamond on the tile you wouldn't find a streak at all, and no not because they consist of the same color, its because the diamond has a hardneess value of 10. So if you have any mineral above the hardness value of 7 you wont get a streak. Did you know that the pencil your using right now to take notes, that pencil is made out of graphite, and graphite is the one material soft enough to leave a streak on paper. Did you know that in some jewelry shops or gold and silver stores they use this test to see if the sellers are actually selling gold or just the fake mineral that looks like gold, Pyrite.
Now on to the last section, Cleavage and Fracture. The way a mineral breaks apart is another way to describe it. If the mineral always breakes along smooth straight edges then it is said to cleavage. Mica as an example is a mineral with cleavage. Seperating the layers of the mineral of Mica is like seperating pages from a book. Not all minerals have cleavage, some have what is called fracture. Fracture would mean that the mineral breaks on rough jagged edges like on another rock or in hard paked dirt. Quartz is an example of fracture, if you try to break it on a piece of wood it wont budge, but if you try and smash it on another rock it would quite possibly break pretty easily.