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Except diamondת which mineral is having high hardness in Mohr scale.

  • A Oxide
  • B silicate
  • C carbonate
  • D phosphate
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closed as off-topic by bon, Daniel Griscom, arkaia, Jan Doggen, plannapus Dec 19 '16 at 12:51

  • This question does not appear to be about earth science, within the scope defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Hello, and welcome to Stack Exchange. This sounds like a homework problem to me; is it? (And, what is "oxide"?) $\endgroup$ – Daniel Griscom Dec 17 '16 at 15:06
  • $\begingroup$ @DanielGriscom this question was asked in IIT geology exam and i have no idea with the option, as i know after diamond , corundum is hardest. Can you please tell me the answer on the basis of option.? $\endgroup$ – Girish Kumar Chandora Dec 17 '16 at 18:09
  • $\begingroup$ I doubt you'll get a good answer here, but I bet if you Google "table of mohr hardnesses" you'll get what you want. $\endgroup$ – Daniel Griscom Dec 17 '16 at 18:46
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    $\begingroup$ I'm voting to close this question as off-topic because it is a homework question and so should show some effort. $\endgroup$ – bon Dec 18 '16 at 9:04
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Although this is a somewhat poorly researched question, I think there is an opportunity to make a nice point here.

First of all, let's look at the Mohs scale:

  1. Talc

  2. Gypsum

  3. Calcite

  4. Fluorite

  5. (fluor)Apatite

  6. K-Feldspar

  7. Quartz

  8. Topaz

  9. Corundum

  10. Diamond

Their (simplified) chemical formulae are:

  1. $\ce{Mg3Si4O10(OH)2}$

  2. $\ce{CaSO4\cdot2H2O}$

  3. $\ce{CaCO3}$

  4. $\ce{CaF2}$

  5. $\ce{Ca5(PO4)3F}$

  6. $\ce{KAlSi3O8}$

  7. $\ce{SiO2}$

  8. $\ce{Al2SiO4F2}$

  9. $\ce{Al2O3}$

  10. $\ce{C}$

What are the anionic groups in each mineral? These are the anions that the metallic cations bond to in the mineral. Let's see:

  1. $\ce{Si4O10(OH)2}$ : hydrous silicate

  2. $\ce{SO4}$ : sulfate

  3. $\ce{CO3}$ : carbonate

  4. $\ce{F2}$ : halide (fluoride)

  5. $\ce{(PO4)3F}$ : phosphate-fluoride

  6. $\ce{Si3O8}$ : silicate

  7. $\ce{SiO2}$ : silicate (although can be regarded as oxide, but it has the silicate framework)

  8. $\ce{SiO4F2}$ : silicate-fluoride

  9. $\ce{O3}$ : oxide

  10. $\ce{C}$ : covalently bonded carbon, no anions here

This should help you find the correct answer.

However, this is only relevant for the Mohs scale. This does not mean, for example, that all oxides are harder than all silicats. Magnesium oxide is pretty soft, for example.

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