2 replies to this topic

[buckland]

I am not a Geologist (retired math/science teacher) but find a lot to be interested in ... and ran across this piece on dolomite. I taught patterning in math class, tessellation, etc. One class captured snow crystals and preserved them on microscope slides to view. Kids love kinesthetic learning.... butterfly nets, goggles, hip-boots anything to make it an adventure. They especially love hammers ... collecting samples and categorizing by attributes.

 

I get all worked up excited when humans apply their curiosity to solve a problem which will benefit all. Answering questions.  This group apparently have done so on that dolomite crystal formation conundrum.  I enjoy reading here posts from the mining folks and enthusiasts about geology ... so here is a piece that might be up your alley.

 

https://scitechdaily...eology-mystery/

 

 

[AWG_Pics]

Very interesting. Many of the geological books and texts I have repeat the vexations over how thick sequences of dolomite could form. This is one of those elegant solutions that makes perfect sense in retrospect. Good science! Thanks for sharing.

[Foy]

Well, let's see--I took Sedimentation and Stratigraphy (the study of how sedimentary rocks form and how their often complex layering occurs) in the Fall semester of 1975 and to whatever extent, if any, the "problem of dolomite" was hit upon in subsequent courses, I don't recall a thing. So now it's been 48 years since I've thought much of the dolomite problem. I only recall that thick sequences of dolomite rock were believed to have been formed by alteration of limestones, where half of the calcium carbonate molecules were replaced by magnesium molecules ---i  other words, CaCO3 became CaMgCo3.  The alteration/replacement was thought to involve large volumes of slightly magnesium rich fluids such as sea water or hypersaline water, but as noted here the process just couldn't be replicated in the lab. I'm delighted to learn that the sterile (clean) environment of chemist's labs failed to shed light on the problem and that it's only been solved when some geologists introduced some spit and mud. Take that, chemists!