Today I went with #Vivianite over #Cavansite for #MinCup23, notably because 1) have you seen that green (next bracket might be a tough choice, as it is pitted against dioptase...) and 2) just found that it was use as a green pigment by Vermeer (thanks @minouette for the information), and that's kind of my current hyperfixation, so...

#vivianite growing in the pore spaces of bones from a 4000 year-old tomb in Sardinia (Rodriguez et al. (2021) J. Arch. Sci. Reports). Phosphate bones plus dissolved iron equals vivianite. #MinCup23 #Archeology

#Vivianite I had to look up last year. It is a blue-green hydrated iron phosphate (Fe2(+II)[PO4]2 x 8H2O) with monoclinic crystal structure and acicular or fibrous aggregates.

But look at this 🤩: #Vivianite pseudomorph after shell from Kerch, Crimean Peninsula, Ukraine (size: 5.6 × 4.6 × 2.7 cm). #MinCup23

📷 Rob Lavinsky, iRocks.com

Oh I didn't explain why light sensitivity got my vote: I too am very light sensitive. At least the #vivianite doesn't get migraines. 🤣 #MinCup23

Now then, I'm probably going to vote #vivianite because sure, it's not very chaotic... but it is *EXTREMELY* light-sensitive. It will start darkening basically the second you expose it to light. Wild, right?

Also, apparently it likes growing on and in fossils and bones. That's just badass. Vivianite for the win. #MinCup23

Hmmm. #vivianite vs #cavansite is not a very chaotic matchup at all - they're both very pretty and fairly rare, the latter moreso than the former, but not very chaotic.

Cavansite owes its gorgeous blue to vanadium, but it's too rare to be a common ore, so it's more usually a collector's mineral. And vanadium isn't really much fuss until you process it, as far as I can tell; just exercise a little common sense in handling, per most minerals. (c) #MinCup23

RT @MineralCup@twitter.com

ROUND 1 MATCH 13

It’s a delight of unusual properties in these utterly unmistakable minerals! Do you favour the ever-darkening green #Vivianite vs the metallic-sour tangy #Sylvite?

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