Volcanic deposits, particularly those rich in ash, can preserve soft tissues through the formation of zeolite minerals. I https://www.quora.com/How-do-volcanic-deposits-like-zeolites-preserve-soft-tissues/answer/Coherent-Market-Insights-1?ch=10&oid=1477743859834156&share=d51dd102&srid=uTm6RG&target_type=answer