#Mystery Specimens
16 messages in this thread
..Well, OK, this one is a well known, not at all a mystery specimen. It is 100%
provably limonite. Blackish cubes, pseudomorphs after pyrite. The books tell me
this is common, yet in my many years as a r-hound, I've never even heard of
such a thing. Beautiful blackish brown specimens, perfect cubes, limonite.
(Trace fluor., Doug, not any in the mineral…)
We *all* have a limonite in our collections. I perhaps recall discussions to
remove the dread beast. BUT have any of you seen such a thing? Cubic
pseudomorphs??? I've never seen such. Not in Harvard, not in the Smithsonian.
Comment? Discussion? (FWIW, the specimens/news comes from a person who is not
versed in the ways of rocks. Please answer to her in a non-technical fashion,
so she understands WHAT exactly we are dealing with in Maryland? Not sure I'm
up on this myself…JayDee the Lost
Hi, Jerry–
Welcome back!
I have not seen any of these limonite-after-pyrite specimens, but I remember
passing on a club field trip where the expected prize was limonite pseudomorphs
after pyrite. It was too ambitious a trip for something non-fluorescent –
perhaps it was the Saline Valley in Calif.? My recall of this one is faded;
sometimes I think UV photons erase data from my memory as they do with EPROMs.
Limonite would be a natural result of pyrite oxidation, thus I am now wondering
why I have never seen such things. Maybe most of the time the limonite is too
crumbly and is washed away?
I sort of expect limonite to be rusty or brown colored. Black and cohesive
puts me more in mind of goethite. How do you tell the difference?
Don't be "lost" so much!
–Doug
Hi Doug-
That's what I would have thought, too, the limonite would crumble and wash
away. I was talking to the person in litforum, and my first guess from her
description was galena. We *all* know what color limonite is. Nope, these are
honest to God black. On the inside, there are pockets of "limonite brown" all
the way to black (and at 17X I would classify some of it as goethite indeed.) –
I suspect somewhere in between limonite and goethite, the majority being
limonite. Allegedly the way you differentiate the two is by the silky
appearance of goethite.
I'm not lost, just lurking slowly (g) – for the past month I've had
*horrendous* line noise and "Sector not found" errors on most CI$ sessions.
Worse, the sectors are there and in good working condition! One time my 'puter
even tried to upload my new novel on the CI$ command line! ARGH!!!
……JayDee the L. ("Lost" comes from Gamers Forum. If you knew how I played
most games, you'd *know* I'm lost most of the time 🙂
Hi, Jerry–
Do you know what sort of matrix these limonites-after-pyrites occur in? Were
they free-standing crystals, or were they packed in solid clay or some such
that might have helped retain the shape?
"Sector not found" that does not repeat for CHKDSK or a disk doctor program to
find and fix makes me itch to rebuild the hard disk starting with a _low_ level
(physical) format – the heads can drift slowly off alignment with the original
formatting, especially if the disk is not in the same attitude as when it was
low-formatted (like when you stand a flat system unit on its side like a
tower).
But I cannot see that causing line noise, so I have to wonder if you have good
enough line filtering and surge suppression.
–Doug
Hi Doug–
Good of my source to send me some specimens in matrix. Haven't got to testing
it. Looks like siltstone, or perhaps "muddy" limestone. Haven't busted out the
chemicals yet. Solidified clay is a best guess at the moment.
>makes me itch to rebuild the hard disk starting with a _low_ level format<
Very concise and well-put explanation of my (irrational, superstitious) fears.
Having dug out my dusty hard-drive papers, I find that a plausible "Sector not
found" cause. A LLF is possible on my SCSI; it was LLF'd at the factory, and
could have been in *any* position. Unfortunately, I don't have a LLF utility.
Naturally, I back everything up. Temporary solution: I get to CI$ from my
Bernoulli drive. Permanent solution: I want a 1/2-Gig NEW drive for Xmas 🙂
Line noise is an entirely unrelated problem (I think) – it's not my lines,
connections or the phone. It started maybe a month ago. Modem or AT&T are the
only possibilities, I think. Line filtering – adequate, or would have had this
problem since day 1. Surge suppression – on my power lines AND modem. Base unit
at wall feeding into a separate power suppressor and modem suppressor. (Did you
guess I *really* like my 'puter?) Lately, for the past 12 hours or so it's
been relatively quiet. Lost an e-mail though.
Will let you know if I positively ID the limonite matrix…JayDee
Hi, Jerry–
OK, the matrix sounds fine enough to hold the pyrite cube shape without adding
irregular impressions. Do you know if the pseudos were completely embedded in
the matrix or partly free-standing?
I am not sure line filtering that was OK yesterday will be good enough today; I
find myself imagining a new factory starting up on your sector of the power
grid and making things worse that way.
It would be agonizing to buy low-level format software and find that the
problem was elsewhere…
I don't think deleting mail after retrieving is automatic with CIS. CIM has an
option to automatically delete after retrieving – I have always had that on,
but noted it for future reference. If I were having trouble like yours, I
would turn it off and suffer having to delete the mail from the CIS (not CIM)
mailbox manually after making sure I had it safely. Hopefully TAPCIS or
whatever you are using has such a selection?
–Doug
Hi Doug-
The matrix is indeed quite fine, and since I can't get it to do much of
anything, I'm convinced it's a mudstone-type of thing. Acid certainly does
nothing. Some of the limonite cubes were completely embedded, and judging by
appearance, would guess they all were at some point, weathering free of the
matrix.
>Line filtering… new factory starting up on your sector of the power grid<
No worry there, all they do is *close* factories around here 🙂 I tried going
by way of Ithaca and managed a 417K download that was giving me *nightmares* on
my local line. I think it's AT&T…
>It would be agonizing to buy low-level format software and find that the
problem was elsewhere<
Problem persists, I think you were right, as it seems only to occur on my
C-drive. Temporary solution: using my Bernoulli disk to access CI$.
No, deleting mail isn't automatic with CI$, but it is with my automation
software, and no way to turn it off. Maybe I should go D/L the latest TAPCIS or
something… JayDee
Hi, Jerry–
What shall we call limonite masquerading as pyrite, "Fool's pyrite"?
Be good and put a new disk drive on your wish list (if the Bernoulli box shares
a controller with that hard disk, it likely is not the controller in trouble);
others of us in this section will be bad and hope Santa fills our stockings
with rocks! 🙂
Have a good Christmas! –Doug
Yay, Doug!!!
Fool's pyrite? LOVE IT! 🙂 The term immediately gets into my new novel on
Cleopatra, who is into (surprise!) alchemy and mineralogy. She's also not the
fink the Romans claimed she was. Nope, not my controller in trouble. Running my
entire system from my controller, including Bernoulli, twin hard drives,
CD-ROM, and lord only knows what.
>others of us will be bad and hope Santa fills our stockings with rocks!<
Umm, well, I could live with that too. Wonder if Santa does rare phosphates??
You have nice Xmas too. Writing (must be on loco-weed or something) LATE on
Xmas eve… See ya shortly, gotta go have another few puffs of loco-weed (G)…
JayDee
PS: A BIG hard disk would not be refused…
jerry,
cleo is a rockhound! sign me up for an advance copy. another author who
hailed from upstate new york and who could really sling a scientific metaphor
was thomas pynchon. could we be getting another gravity's rainbow? maybe with
enough loco-weed?
merry christmas.
nathan
Hey JD,
Lost but not forgotten. Limonite pseudos after cubic pyrite are dirt common
in SE Pennsylvania. You can find them in most limestone quarries here, and
there are some well known farmers' fields in Lancaster County, where you can
find the pseudos. Just north of Lancaster, there is a locality where the
limonites occur as pyritohedrons.
Cheers!
Nathan
Hi Jerry,
Yes, very common, in fact probably extremely common! You probably haven't seen
limonite ps. of pyrite much because most people consider them boring and they
aren't exactly highly aesthetic, so not prominently displayed.
But they are very common. There are millions (probably many more zeros than
that) in siltstones, sandstones and the slightly metamorphosed equivalents of
these, and possibly in other geologic environments. In my area (N. Idaho) and
in neighboring Montana we have hundreds of square miles of boring 1.4 billion
year old metasediments of the Belt supergroup (mostly fine grained silt size to
sometimes sand size grains). Many of the layers have these little critters in
them, moslty <4 mm or so but up to 4 cm or more. Mostly as cubes, sometimes as
pyritohedrons. They are mostly completely altered to "limonite", but vary from
completely altered to partially altered to fresh pyrite with only a thin brown
skin.
As Doug states–black would suggest goethite. That is true, while in college I
x-rayed these pseudos from several localities. They were all brown or black on
the surface but black inside and all checked out to be goethite.
Well known localities include Pelican Point, Great Salt Lake, Utah and Tekoa
Mountain, Whitman County, Wash. At both localities they occur as sharp cubes to
4 cm or more, sometimes in clusters.
For your non-technical friend: They are common because pyrite easily oxidizes,
in the right environment the pyrite is oxidized with the sulfur being released
(lost to the immediate system, my guess is it goes into "rockspace" which is a
cousin to "cyberspace" which we all know is where lost e-mail messages and data
go) and the iron combining with oxygen and hydroxyl ions forming crystalline
goethite which replaces the pyrite crystal, retaining the crystal shape of the
original pyrite. If the environment is not right for this, then the pyrite
oxidizes to the "non-crystalline" form of limonite, generally leaving a rusty
lump, not a sharp pseudomorph of the pyrite.
Where does all the sulfur go? In nearly all the environments, you have
oxidation altering the pyrite to goethite/limonite and the sulfur is gone. I
know of only one site where the pyrite is altered, but remains shiny with no
rust attached but only elemental sulfur (a reducing environemnt?).
Lanny
Hi Lanny-
I guess I just don't get to the right areas or something. You'd think I'd have
seen something like that in the field… Wanna swap boring areas? (g) Never
been in your area, it's GOT to beat miles of Devonian shale and fossils…
Yes, goethite is indeed present, I think that's why the black. Inside, they
range from "limonite brown" to black, including powdery areas.
Good description for my non-technical friend – I can't find *where* I saw it
when researching these things, but as for where the sulfur goes, FeS oxidizes
to ferrous sulfate, which then releases the sulfur as sulfuric acid, and from
there on into "rockspace."
>Cyberspace, where lost e-mail…goes<
Lately, the bit-bucket must be *full* of stuff from me, especially on CI$. Got
a leprechaun in my 'puter or something. Actually, since this *is* Geology
Forum, it must be a kobold 🙂
A reducing environment??? Elemental sulfur??? Where? That has all kinds of odd
mineral possibilities! Not unheard of, since you *do* hear of things like
native arsenic and mercury… JayDee the L.
Hi, Jerry – good to hear from you.
> "rockspace."
> >Cyberspace, where lost e-mail…goes<
I thought I heard something a few years ago that someone had found about 5
terabytes of lost e-mail in an abandoned warehouse somewhere in New Jersey.
Supposedly the warehouse was scheduled for demolition so the data was loaded
on a large ocean-going barge and sent off for disposal. Since nobody would
accept the 'toxic' waste, the barge is _still_ cruising about the world. <G>
Must have been from one of the April 1rst issues of one of the trade journals.
<g>
H'mmm, I wonder if any of the socks my drier ate are on that barge?
Cheers, Guy
Hi Guy-
ROFL!!!! I'm sure some of *my* socks are on that barge. As well as a few gigs
of *my* e-mail. On the serious side, I find out that if you leave your mailbox,
any deleted messages are lost *forever*. Scenario: Use your favorite navigator,
tell it "Get the mail. Fetch, boy." It does that, precisely. Because of line
noise, it gets saved to never-never land, and logs you off. Guess what gets
loaded onto the barge??? CI$ doesn't save your mail for one millisecond after
it thinks you have it. ARGH!!! …JayDee the L.
Jerry,
The locality I mentioned is in the N. Cascades of Washington and is a breccia
body in diorite (or whatever similar rock it happens to be). I have not been up
to it, and the location has been kept secret. I did manage to direct a couple
friends to the sources of rumors from a hunter and a fisherman. Each of which
gave my friends information which allowed them to find the spot independantly
of each other. Since then, it has alwyas been on our to do list, but it is a
long grueling hike up steep brushy forested ridges and we just haven't gotten
up there together. In fact, they went once and aren't too crazy about trying it
again.
As exposed, the locality is an exceedingly steep mountainside (nearly need to
rope up to stay attached). It is very rusty red on the surface (sounds more
like a typical oxidized mineral occurrence) and one can dig in the soil/rock
and find quartz crystals, sometimes in clusters, generally fairly nice or
frosted. The pyrite occurs as slightly rusty cubes or shiny "etched" and
rounded cubes. Some of these shiny ones contain holes, in fact one piece was
loaded with holes and tubes. These can have nice yellow sulfur powder or
possibly tiny crystals in the holes.
This is a locality that I first learned about in the early 1970s and finally
traced down enough stories/rumors to direct my Washington friends to the right
people that they got up there in the late 1970s. Now that I am older than I
felt then, I had better either make the nasty hike/climb up there soon, or I
wont' ever feel like trying it.
Lanny