An Article In Meteorite-Times Magazine
by Robert Verish
An Article In Meteorite-Times Magazine
by Robert Verish
April 1998
Looking Back 10 Years Ago
It's interesting how certain things can jar your memory. Like when a recent event reminds us of something that we have long forgotton.
Well, something like that happened to me recently. It was while reading about the Franconia Area H-metal meteorites (a.k.a., Sacramento Wash 005) when I remembered about some small iron "beads" that I had found back when I was first metal-detecting the Gold Basin area.
But, just in case you are not familiar with the term "Franconia Area H-metal", this is the name that has been used to describe the numerous, small iron meteorites that have been found both north and south of the Sacramento Wash, near Yucca, Arizona. Two of the larger specimens of these "irons" were submitted by Larry Sloan and Jim Smaller to the University of Arizona for classification. They were classified as "H-metal" and were assigned the now formally-approved name, "Sacramento Wash 005". It is the general consensus among the finders of these small irons, that they were formed by spalling off of a fragmenting Franconia Area meteorite, AS IT FELL. Most likely it was during the fall of the Franconia (H5) meteorite, but this has not been conclusively proven.
While trying to form a mental image of an incandescent H-chondrite meteor vaporizing in the upper atmosphere, and trying to figure out what forces were at work that would melt or rip apart metal veins into little iron fragments, my memory was jarred with the recollection of having found these odd iron beads at Gold Basin, Arizona. But, they're not really "beads", meaning that they didn't have a hole drilled through them. But they were bead-shaped. To be specific, they were oblate spheroids, meaning that they were flattened spheres. Not that they were all the exact same size and shape, as if a handful of ball-bearings were thrown out onto the desert surface, but as if molten droplets of iron were allowed to cool and solidify while still spinning, thus forming flattened spheres. In order to form this way the molten droplets would have to be suspended in air, or drop through the air a sufficient distance and time until they became solid. Because, unlike the lead musket balls that were produced during the 19th century-era "shot towers" (in which molten droplets of lead were dropped from the top of a tower and solidified before they hit a vat of water), these iron balls show a little deformation by having come in contact with the ground.
In any case, take a look at the images below.
I looked hard for the original pictures that I took of these little iron balls, but all that I could find remaining was just one image. That image was my attempt at trying to show the etch-pattern that I had made on the flat surface that I had ground-down and polished on one of the iron beads. The etch that was produced on this flat surface had a very fine, dendritic pattern. It was so fine that it required a low-power microscope for examination. I took several images through the eye-piece of the microscpe, but they are of poor quality (this was back in April of 1998). For the reader's convenience, I've taken a more recent image (April 2008) and it can be viewed HERE.
While searching my files for these images, I noticed that they were "created" way back in April of 1998 - exactly ten years ago!
>BR>
I started searching for other images and documents that were "created" or "modified" at that time period.
As it turns out, these web pages are STILL on-line! Given the short life-time of most web pages, browsing a website that is over 10 years old is like uncovering a "virtual" archeological site. And as you can imagine, these old web pages are quite out-of-date. But anyway, here are the links to them:
The following images are 10 years old, which explains why they are low resolution, but they depict the kinds of topics that we were interested in at that time:
Below - Gold Basin iron artifact/bead(?):
the original image taken in April of 1998 of the coffee-bean-sized iron bead that was ground, polished, and etched!
Above image taken by R. Verish, Mar-Apr 1998.
Below - Gold Basin iron artifact/bead(?):
the original close-up image from 1998 showing the "dendritic" etch-pattern!
Above image taken by R. Verish, Mar-Apr 1998.
Below - Gold Basin iron artifact/bead(?):
a recent image of the iron ball that was originally etched in 1998!
Above image taken (recently) by author, R. Verish (April 2008).
Below - Gold Basin iron artifact/bead(?):
a recent close-up image showing the original etch-pattern from 1998!
Above image taken (recently) by author, R. Verish (April 2008).
Below - Gold Basin iron artifacts(?):
a view of all of the iron balls!
Above image taken (recently) by author, R. Verish (April 2008).
Below - Gold Basin iron artifacts(?):
a view of their "bottom-side" shows that some beads are flat on that side!
Above image taken (recently) by author, R. Verish (April 2008).
Below - Vaca Muerta:
a classic example of a mesosiderite - it's metal portion can produce an ETCH! -
Vaca Muerta - image taken by R. Verish, Mar-Apr 1998.
Below - Canyon Diablo:
a rusty slice with a nice graphite/schreibersite nodule that needed to be "re-etched"!
Canyon Diablo slab - above image taken by R. Verish, Mar-Apr 1998.
Below - Ibitira:
a peculiar eucrite - it's called a "vesiculated meteorite"! It was during this same time period that I became intrigued by meteorites that contained vesicles. Particularly if they contained euhedral crystals such as this one.
Ibitira - above image taken by R. Verish, Mar-Apr 1998.
Below - Mt. Tazerzait:
a peculiar chondrite - it's "vesiculated" and is S1 - very low shock stage! It was during this same time period that I became intrigued by meteorites that contained vesicles.
Mt. Tazerzait - above image taken by R. Verish, Mar-Apr 1998.
Below - Mt. Tazerzait:
This meteorite is so intriguing I purchased a slice back in 1998!
Mt. Tazerzait - above image taken by author April 2008
It was during this same time period that post to the Meteorite-List continued the discussion about the recent fall of the Monahans meteorite. But for the remainder of the month of April in 1998, the majority of post were tektite-related.
Set of Tektites - above image taken by author in April 2008
Hopefully, you find my reminiscing of the "good ol' days" to be of some interest. Maybe this will give the reader an opportunity to pause and remember events from a decade ago, as well, and consider how we all arrived here at the present. At least, it gives us some idea of where we were, and what we were doing 10 years ago.
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Bolide*chaser
It was interesting what I found. It was like taking a trip back in time. It brought back a flood of memories.
It reminded me of the early days of the Meteorite-List, where I would speak of myself as a "newbie" and would ask all of the typical newbie questions. I was already searching for meteorites, but I was still learning how to identify meteorites. This was back at a time when I coupled the writing of my field trips with my other new hobby, writing web pages. Looking at my files and images from 10 years ago, it appears that around March and April of 1998 I was very active at making web pages describing my search for my first meteorite find at Gold Basin.
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This etch pattern is evidence that the metal is an alloy.
The very fine pattern of the etch is evidence that this metal had solidified very quickly. Consequently this iron's etch pattern doesn't match with any etch pattern from an iron meteorite. So, for the past 10 years I've set these oddities aside and labeled them as "artifact (?) iron". But it was recently brought to my attention that this "quenched-pattern" doesn't necessarily preclude that these iron balls didn't come from an iron meteorite. Meaning that, given this scenario, if an iron meteor/meteorite were heated sufficiently to melt, and if this partial-melt was allowed to flow away to form droplets of molten iron, and if these droplets were allowed to solidify while retaining their near-spherical shape, there is no reason that the resultant metal wouldn't look just like these iron balls and that it would result in this "herringbone" etch-pattern.
So, I'm back to square one.
But now, my next step is to analyze it for percentage of Ni content.
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This microscopic etch shouldn't be called a Widmanstatten pattern, but it is evidence that the metal is an alloy of iron and nickel. The etch pattern is evidence that the molten alloy had time enough for the Fe and Ni to start to segregate as it solidified. The shorter the time that the metal solidifies, the finer the pattern. In the case of my Gold Basin iron balls, that molten alloy was essentially quenched, producing a very fine, dendritic pattern.
CLICK on the image below in order to see close-up images of the etch-pattern.
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http://www7.pair.com/arthur/meteor/archive/archive4/April98/maillist.html
VAPOR DEPOSITED MINERAL ASSEMBLAGES IN VESICLES OF THE EUCRITE IBITIRA.
authors: M. Wadhwa and A. M. Davis.
These photo's by "Microman108" are of the micro impacts he found on a few of the irons that he recovered out in the Franconia Area in April 2005.
My previous articles can be found *HERE*
