What are these minerals?

[Mark1955]

Found in a mine recently. Much is rust colored granules with many whitish leaf type growths... I've use the S&S Minerals book to try ti identify it but it leaves more questions than answers. I have no idea what it is... does anyone here?
This speciman is about 3" by 1.5 inches and the largest points Thanks for any insight!

[rhartill]

How hard are the blades [leaves]?

http://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness

depending on hardness could range from mica to calcite but probably barite:

http://www.baritespecimenlocalities.org/Assets/WebPhotos/WebPicsCAN-MEX/BariteMEXCongresoLeonBealsAWeb.jpg

The brown weathered parts are probably oxided pyrite which has turned to limonite.

There's a neat book on interpreting the weathering that has occured:

http://www.scribd.com/doc/13343701/Interpretation-Leached-Outcrops-Blanchard

colored pictures appear in this volume towards the back of the book...

but please do tell where this was found...

[Mark1955]

Thanks Russ for those links... some very interesting stuff there. The leaves are fairly difficult to break off with one's fingernail. I'll IM you for now as to where it was found. Amazing place to say the least!!!

Mark

[ryan162]

wow thats neat looking. you guys may turn me into a rock hound yet lol

[cherokeepilot85]

It looks like you have a nice piece of either barite or hemimorphite. I would need to look at it under a hand lens to be sure.
Would you please PM with more details and where you found it. If I know where you found it that may narrow down which of the two it is.

Thanks

[Stuart]

Wow! that is a nice specimen, I actually have a couple peices of the same stuff, but they are not quite as nice. What I really think is impressive is the photo... man that is a sharp picture! What camera/lens did you use?

I think I know which mine you found it in so I won't ask about that

[cherokeepilot85]

After you gave me the mine info I did some research and your mineral sample is definitely Barite.
Thanks for the PM and the info.

[Mark1955]

You'll be shocked! The camera is my Canon Rebel XTi. The el cheapo lens that came with it zoomed in to about 55mm, and a cheap desk top high intensity lamp and the camera's flash lighting the speciman. The Rebel has 10 mega pixels so you can crop out the rest of the gobbledigook and just post the mineral itself and it stays reasonably sharp. I'm not a big fan of Macro Lenses... no depth of field at all.

Here is another I did in just a few min. Now I'm wonderin what that redish brown coating is???

[Stuart]

Now that is how you make the best of what you've got! I would have guessed you shot it with a 5D and an L series lense.. Those rebel xti are actually really solid cameras I would recommend them to anybody wanting to get into digital photography. Do you want to come over and shoot some of my rocks?

[Derek]

Stopped down Macro lenses can give a decent amount DOF and with Helicon Focus or similar software that let you make a composite image from several images you can get awesome DOF.

[Mark1955]

Yes, they can to a point. However macro lenses are designed to focus on flat objects. All lenses exhibit some but differing amounts of depth of field... I worked at CANON for a good many years back in Chicago as a lens tech repairing mainly TV camera lenses but when it was slow I also did still camera lenses as well and worked on many of the 55 and 100mm macro lenses they made. Macros can have extremely high resolving power exceeding 80 line pairs per mm and you'll generally find the sharpest resolving power in line pairs per mm in any lens is at the middle f-stop range... f5.6, 8 or 11. The first macro lenses built go back to the 1930s and were used on optical printers in film labs...mainly for special effects work. They were designed to focus on another film plane. Never heard of the software you mentioned... I'll have to check that out!! Thanks for the tip.

Mark