Mindat Logo

Marcasite Decomposition

Posted by Brian Kulwik  
Brian Kulwik
Marcasite Decomposition
March 02, 2012 10:36PM
I have some specimens of what I believe to be marcasite, in many forms--concretions, crystals, and stalactites--that I found in one locality. Some of these are undergoing decomposition, forming into white crystals and falling apart, especially the stalactites. I was wondering if anyone knew why some of these were decomposing and others are not, and if there is any way to stop them. Once they start to get the white crystals, it is about six months before they start falling apart and one to two years before they become a pile of white powder...

Also, does anyone know if these are of any value (the ones that are not falling apart...) I have bags full of concretions, marcasite??? stalactites, and marcasite/pyrite crystals, and I was wondering if these would be worth my time to try to sell. If so, where would I go about doing this?

Thank you very much.
open | download - P1010499.JPG (417.3 KB)
open | download - P1010502.JPG (690.8 KB)
open | download - P1010493.JPG (555.8 KB)
avatar Re: Marcasite Decomposition
March 03, 2012 12:49AM

check this out, maybe it'll help (pyrite/marcasite decay in fossils): [www.sheppeyfossils.com]

Re: Marcasite Decomposition
March 03, 2012 04:58AM

Have you seen the long thread "pyrite disease" from a few months back. Very informative.

Brian Kulwik
Re: Marcasite Decomposition
March 05, 2012 04:05AM
Thank you guys for the helpful links!

Your Email:


  • Valid attachments: jpg, gif, png, pdf
  • No file can be larger than 1000 KB
  • 3 more file(s) can be attached to this message

Spam prevention:
Please, enter the code that you see below in the input field. This is for blocking bots that try to post this form automatically. If the code is hard to read, then just try to guess it right. If you enter the wrong code, a new image is created and you get another chance to enter it right.
Mineral and/or Locality  
Search Google  
Copyright © Jolyon Ralph and Ida Chau 1993-2014. Site Map. Locality, mineral & photograph data are the copyright of the individuals who submitted them. Site hosted & developed by Jolyon Ralph. Mindat.org is an online information resource dedicated to providing free mineralogical information to all. Mindat relies on the contributions of thousands of members and supporters. Mindat does not offer minerals for sale. If you would like to add information to improve the quality of our database, then click here to register.
Current server date and time: December 20, 2014 22:17:19
Mineral and Locality Search
and/or Locality:
Fade toolbar when not in focusFix toolbar to bottom of page
Hide Social Media Links
Slideshow frame delay seconds