Kai loves mineralogy - This project is simple: make our own mineral samples at home (ha! simple...)
#1: Melanterite
Melanterite
Category: Sulfate Mineral
Crystal Symmetry: Monoclinic 2/m prismatic
Color: Green, pale green, greenish blue, bluish green, colorless
Crystal Habit: encrustations and capillary efflorescence; rarely as equant pseudo-octahedral, prismatic or tabular crystals
Crystal System: monoclinic
Cleavage: {001} perfect, {110} distinct
Fracture: conchoidal
Mohs scale: 2
Luster: vitreous
Streak: white
"Melanterite is a hydrated iron sulphate formed after the decomposition of pyrite or other iron minerals due to the action of surface waters. It is often found in mines as a post-mining formation on mine walls."
Color: Green, pale green, greenish blue, bluish green, colorless
Crystal Habit: encrustations and capillary efflorescence; rarely as equant pseudo-octahedral, prismatic or tabular crystals
Crystal System: monoclinic
Cleavage: {001} perfect, {110} distinct
Fracture: conchoidal
Mohs scale: 2
Luster: vitreous
Streak: white
"Melanterite is a hydrated iron sulphate formed after the decomposition of pyrite or other iron minerals due to the action of surface waters. It is often found in mines as a post-mining formation on mine walls."
beautiful sample!
I was initially uncertain as to the identity of the blue crystals I found.
What is it?
I don't know.
How do I find out?
Well, I guess I can start with what I know about it...
101 time: How hard are the crystals?
Pretty soft, they almost seem to smear.
Where did I find them?
Underground, in the roof (back) of an abandoned mine stope.
What is the crystal form?
Geez, half these things are crushed and too tiny to really pick out the form of a single one of the crystals... Okay then, what is the crystal habit?
Druzy! A fine mat of shimmering blue crystals covered the rock where it was exposed to the air.
Only where the rock was exposed to air?
Why, yes, I guess that means it must have formed after the stope was made. Overall, relatively quickly, geologically.
What was the environment like?
Wet. The underground was filled the constant sound of dripping. And not particularly warm, either.
Why is THAT rock so special, why not form on some other rock?
On closer inspection of the rock (SEE: Smashing it open) I am able to see heavily oxidized cubes of iron pyrite, an iron and sulfur mineral.
Put it together....
Okay, formed really quickly in a really wet environment? Probably some water in the structure. Formed exclusively on the iron pyrite bearing rock? So probably some iron or sulfur or both in the structure.... I have enough to start searching MINDAT.
time passes
Here we go! It looks like it is probably melanterite, I have the right environment, the crystals look about right. It says it is poisonous, I think I will forego a taste test. Ah! If I let it dry out, it will form a white powder which can be re-hydrated, or if I put it in sufficient water it can be dissolved and re-precipitated by evaporation.
I proceeded to crush the rock and steep it in boiling water to react a little more of the iron pyrite and have since been working on filtering to get rid of impurities as well as dissolving and re-hydrating to form larger, more gorgeous crystals.
-Kai
After the first pass at recrystallizing the minerals we decided to try again. It is humid in our little cabin so it is a slow process, but we are hoping that means we will get some nice big crystals!
~Kathleen and Kai
