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Rock/Crystals Identification

Comments

  • #2
    the keen edge
    Closed Accounts Posts: 1,533 ✭✭✭the keen edge


    From the photographs I'd suggests that it is either Quartz or Calcite.
    To disgusting the two minerals:

    1) Pour HCl acid on it, more likely you'll use vinegar (as a weak acid). If your rock fizzes then it is calcite, the fizzling is CO2 being liberated. If your rock does not fizz then it is quartz.

    2) Scratch your rock with a cent coin. If the coin scratches the rock then it is calcite. It has a much lower hardness than quartz. If the rock does not scratch then you have quartz.


  • #3
    Step23
    Registered Users, Registered Users 2 Posts: 131 ✭✭Step23


    You are right, it's quartz, 100% sure, but I'll give you the reasons why, the crystals are hexagonal and terminated (go to a point) and your sample shows typical conchoidal fracturing which is characteristic of quartz. When you break calcite it just breaks into smaller cubes (this is known as cleavage, where it breaks along planes of weakness in the mineral, quartz doesn't have any planes of weakness in its structure so it fractures).

    Sadly you are also right about the specimen being worthless, regardless of any value you found it yourself so, I'd be happy enough with that :)

    The advice the keen edge gave is a good way to distinguish the two minerals, which people often get mixed up with.


  • #4
    taytothief
    Closed Accounts Posts: 450 ✭✭taytothief


    Thanks for the replies guys, much appreciated. :)


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