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Let's Rock => Identifications of Materials => Topic started by: 55fossil on December 10, 2018, 09:14:08 AM

Title: Marcasite or Pyrite in Graveyard Point Plume
Post by: 55fossil on December 10, 2018, 09:14:08 AM

     Without a microscope to view the structure I have no idea how to distinguish between marcasite and pyrite in agate. Seeing as this makes a roostercomb like cloud I think it is marcasite. But I also see what appear to be golden pyrite cubes. Possibly both, I have no idea. Here are two images to ponder. Please help identify.

Title: Re: Marcasite or Pyrite in Graveyard Point Plume
Post by: yukonjade on December 10, 2018, 10:50:15 AM

 Marcasite has the same chemical formula as pyrite but has a different structure.

Title: Re: Marcasite or Pyrite in Graveyard Point Plume
Post by: gemfeller on December 10, 2018, 12:15:29 PM

One way to differentiate them according to my old mineralogy textbook is to soak a specimen in a strong nitric acid solution.  Pyrite gives no reaction but marcasite gives off excess sulfur, leaving the solution cloudy. In a dilute nitric acid solution some bubbles may be observed.   

Title: Re: Marcasite or Pyrite in Graveyard Point Plume
Post by: Redrummd on December 12, 2018, 09:30:09 PM

Looks like mostly marcasite with a bit of pyrite mixed in.....