Quartz has the chemica formula SiO2 and although nearly pure does contain impurities such Fe, H20 or Ti. Yet none of these are reflected in its formula.Presumably Quartz could be written for instance as (Si,Fe,O2) but it is never shown like that. Yet compared to say Olivine its formula is written as (Mg2,Fe2 SiO2). Why? Any help would be appreciated as I am new to this area!
2007-03-17 10:36:48 · 5 answers · asked by Gideon 1 in Science & Mathematics ➔ Earth Sciences & Geology
The impurities in quartz can be inclusions that don't necessarily combine with the quartz crystal lattice. They can simply be inclusions in the material not bonded to SiO2 tetrahedron.
In the case of olivine, the Mg and Fe are the two minerals that can fit into a certain site in the olivine lattice. The amount of Fe and Mg relative to each other is how we get eith Fayalite, which is the Fe rich endmenber and Forsterite, the Mg rich endmember. The Fe and Mg are built into the olivine. The impurities in quartz are not necessarily built in, but present along with. Thats why quartz has the same properties (shape, etc) but is just a different color.
2007-03-17 12:09:42 · answer #1 · answered by sprocket9727 3 · 3⤊ 0⤋
Out of all the answers given to this point, Sprockets is the only one to get it right. The truth is that there is no chemical variability to quartz, none whatsoever, it is simply SiO2 and nothing else. Chemical inclusions commonly occur, but they are not part of the quartz crystal.
2007-03-18 12:34:59 · answer #2 · answered by Amphibolite 7 · 0⤊ 1⤋
it has to do with the chemical's combining. Often when you combine chemicals as you might know, the written formula changes. In olivine it may contain the same chemical in quartz therefor it is in the formula and the impurities in quartz may alter it.
2007-03-17 10:40:53 · answer #3 · answered by mimi2424 2 · 0⤊ 2⤋
It's called ionic substitution. Sometimes atoms of similar size and valency can be substituted within the crystal lattice. These impurity's can cause a slight change in colour or appearance. The amount of substitution can sometimes be noted in the chemical formula, but is often not due to there being more than one substitution taking place.
2007-03-17 11:27:59 · answer #4 · answered by Professor Kitty 6 · 3⤊ 1⤋
Quartz is an important mineral in igneous rocks and some metamorphic rocks. Igneous and metamorphic rocks were created by the intense pressure and heat of volcanic activity. Their impurities vary. When it is written (Si, Fe, O2), this refers to an igneous rock, of which quartz is an important part. Therefore, the formula does not reflect quartz, but a rock of which it is a part.
2007-03-17 10:52:16 · answer #5 · answered by Anonymous · 0⤊ 4⤋