In the mineral identification questions, we commonly need information in addition to the hardness test suggested in our guidelines. In particular reactivity with acid and streak tests can be important.

It is easy enough to describe how to do a streak test on unglazed ceramic (eg the foot of a plate or cup) but I'm a bit nervous about suggesting people use HCl. The 'muriatic acid' from hardware stores is about 31% according to the web so even that should be diluted 1:2 acid:water. Although I'd be comfortable neutralizing acid with sodium bicarbonate for disposal, I'm not sure I'm comfortable explaining to others - especially since there (worst case) would be varying local regulations.

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    $\begingroup$ Yeah, acid tests would be really helpful but I'm not really sure many people would think of doing it -- most people probably don't have HCl lying around (even the diluted one you pointed out). $\endgroup$
    – hichris123 Mod
    Jul 7, 2016 at 2:43
  • $\begingroup$ I would also see a problem with respect to proper handling and disposal of acids. Would using citric acid or something similar be an option? $\endgroup$ Jul 18, 2016 at 11:21
  • $\begingroup$ I think this question/discussion would be better merged into meta.earthscience.stackexchange.com/questions/124/… $\endgroup$
    – naught101
    Jul 20, 2016 at 1:39
  • $\begingroup$ I think additional test descriptions should be placed there but this meta-meta discussion should stay separate to keep that clean for new members $\endgroup$
    – haresfur
    Jul 20, 2016 at 4:18


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