"Hi Bob,

Beautiful plate. What are you hoping for?

Thanks,

Aaron"

"I think its gorgeous just the way it is. I noticed something different about that plate. Its lighter yellow towards the base, and rustier towards the tips. Is that Sulphur? Or just an illusion from mud?"

"As you guys know, Limonite is not a true mineral but a mixture of similar hydrated iron oxide mostly goethite with lepidocrocite, jarosite, and others. . Most of limonite is made up of Goethite. Massive Goethite and Limonite can be indistinguishable. It easily changes to hematite with a loss of water. Yellow is a common color for limonite and is used as a pigment called Yellow ochre, ( Fe2O3 • n H2O.) Red ochre, (Fe2O3), is the anhydrate of yellow ochre, which turns red when heated, as this drives off the water ligands.Changes in water content changes the color. When I speak of changes in water content I refer to chemically bound water not just mixing water with the material.
With that said thanks for the recipe. By the way the agate slabs you sent me; rainbow when back lit, They look similar to the Horse Mountain picture I posted.
Bill
"

"The mud is mud, a mixture of decomposed granodiorite (clay) and iron oxides (limonite). The iron compounds in it replace lots of stuff at Spruce ... other minerals, tree roots, rodent poo. Yeah, we have real coprolites at Spruce, in intrusive igneous rock, no less! The limonite component of the mud makes all these wonderful things happen. The limonite is a break-down product of pyrite, produced by a bacteria which eats the pyrite. Thiobacillus ferroxidans, no friend of mine. If only someone had injected a big syringe of penicillin into Spruce about a 10,000 years ago, all the pyrite would be shiny.

Can't tell from the photo what your crystals are, but given the parameters, I agree with Zeke: likely calcite. Look for cleavage under magnification, or drop a tiny piece in acid.
Bob"

"You got that thing clean up yet Bob?? Huh, do ya HUH??? lol"