# identifying potch stone

**URL:** <https://boards.straightdope.com/t/identifying-potch-stone/668819>\
**Category:** Factual Questions\
**Created:** [September 14, 2013, 3:52am UTC](https://boards.straightdope.com/t/identifying-potch-stone/668819 "2013-09-14T03:52:55Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\
**Post date:** [September 14, 2013, 3:52am UTC](https://boards.straightdope.com/t/identifying-potch-stone/668819/1 "2013-09-14T03:52:55Z")

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We got a map for rock picking at a rock shop, and one of the locations they identified said we could find a variety of opal there, from potch (common opal) to the good stuff. We found a bunch of nice rock there, some of which appeared to be fragile stone in caliche (much of it opaque, some translucent). Thing is, I am not sure whether I am seeing actual caliche with opal/potch or some kind of crusted chalcedony. Can anyone tell me how to identify opal?