Tuesday, March 17, 2009

Happy St. Patrick's Day!

Surprise: a rock with a green mineral in it!

This is a very heavy rock containing three copper minerals: the green one, malachite, a black one, and a reddish-pinkish-purplish one. Large blue squares in the background are centimeters.
A close-up view of said minerals. The little orange bits - which I have to throw in for Alaska Al, who says he isn't from the green part of Ireland - are probably a goethitic Fe-oxide.
Here's the backside of a rock, where some of the malachite crystals can be seen a bit more readily. The bright reddish orange may be a mix of goethite and some other oxide mineral, except for the lower orangey blob, which is part of my finger. The faintly bluish mineral in the bottom center might be chrysocolla.

[How can you tell which side is the frontside or backside of a rock? Simple, the frontside is either the first side you look at, or it's the side facing up when the rock is on the ground or on your display counter. The backside is the other side.]

What are the sooty black and the shiny reddish-pinkish-purplish minerals?

13 comments:

Cath@VWXYNot? said...

Nice topical post! I have no idea what the other minerals are, but I'm wearing green and am just a couple of hours away from my first beer of the day.

Lockwood said...

I have a damnably hard time distinguishing anything about minerals from photos, though obviously that hasn't stopped me posting my own pretty rock pictures. ; ) But from context, I'll guess the black one is pyrolusite (Mn oxide) and the purple-pink one is bornite. Hmm... bad pun alert... I'll post it on my own blog after I kick it into shape.

Amanda@Lady Scientist said...

The rocks are very pretty. Unfortunately, I don't know anything about rock minerals :-)

Silver Fox said...

Ding ding ding... Sorry, wrong answers!

The sooty black mineral is a very high grade copper mineral.

The pinkish-reddish mineral is a high grade copper mineral. I could not see any native copper in the rock, but it has a very high density.

Silver Fox said...

Cath, did you have a green beer?

Amanda, as Lockwood said above, it's actually kind of hard to determine minerals from a photo.

Lockwood said...

Hmmm... the MnO was a stab in the dark, but I felt pretty good about bornite. Using the interwebz feels like cheating. I'll give it a little more thought.

andrew said...

The red one must be cuprite.

Silver Fox said...

Yes! We have a winnner: Andrew! The red one is cuprite, which often is intergrown in this particular supergene to oxide environment with native Cu.

Now, what is the sooty black copper mineral? Hint: it's sooty, and black.

Lockwood said...

I hereby recuse myself from further guessing; I wanted to find a good reference for bornite and came across two good candidates; one simple question would narrow that to one. However, as I warned earlier, thinking about this triggered a bad pun. It's an illness, I know. I can't help myself.

Cath@VWXYNot? said...

"Now, what is the sooty black copper mineral? Hint: it's sooty, and black."

Is it soot?

Silver Fox said...

Cath, a good guess considering all the times I've hinted at soot. Soot, though, is made of Carbon, C, and this mineral, while sooty or soot-like in texture and color, is a copper mineral with Cu in it.

Any copper geologist would get this supergene mineral right away. There are only two minerals that this could be as far as I know, but one is more common or more commonly cited, anyway.

Cath@VWXYNot? said...

It wasn't actually a serious guess ;)

Silver Fox said...

Oh, hey - the black sooty mineral is chalcocite. Contains a lot of copper.