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Difference Between Holes, Cavities, and Vesicles in Meteorites

When people think they have found a meteorite, much more often than not, what they found is actually a terrestrial rock, often referred to as a meteorwrong. These rocks come in all shapes, sizes, colors and textures, and sometimes include holes. In posting these specimens for review, they may be told that “meteorites do not have holes”. Though generally true, this statement misleading because a simple internet search will uncover images of actual meteorites with holes. This article is written to clarify this issue.

Though our definitions for holes and cavities differ somewhat from the dictionary definition, they are better descriptors than what is normally used to describe meteorites.

Holes can be caused by ablation or various types of terrestrial weathering and generally describe a void that extends all the way through a specimen.

Cavities can also be caused by ablation and in that case are called regmaglypts, or by the weathering of softer or more degradable material within the meteorites such as troilite in iron meteorites.

 

Vesicles are caused due due trapped gases expanding within the molten material/melt at its time of formation and are rarely bigger than a few millimeters, though in extremely rare cases one or two larger vesicles can by be larger. Vesicles inside meteorites do not occur due to its voyage through our atmosphere, though bubbles/vesicles can form on the outside crust during entry.

Ibitira eucrite meteorite with vesicles.
Tissint Martian shergottite with vesicles in shock melt veins. Image Credit: Mendy Ouzillou
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How to Start a Meteorite Collection

Michael Kelly:

My recommendation is you start up a catalog now keep track of important info on your collection when you bought it total weight total cost, details of why it interested you etc. if you keep at it it’s hard to “catch up” on details later. The little nuances you might forget in a piece in 3 decades or 400 pieces later

Greg Stone

Please categorize any and all new specimens collections – keep records, I am truly sorry I didn’t when I was purchasing prior 10-12 years ago. Now I just have a mess of things I am now trying to rectify

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Classification Punctuation for Chondrites

The Meteoritical Bulletin is filled with incredible meteorite-related information. However, even the most experienced collector might be puzzled when evaluating a classification and trying to understand the various punctuation used by the Nomenclature Committee. For example, do you understand the difference between an L/LL3 and an L(LL3)? Please note that the punctuation only covers chondrites. There is little carryover into the achondrites, irons and stony-irons, and within these other groups, there are discrepancies.

Meaning Behind Punctuation in Chondrite Classifications:

G = chondrite group (H, L, LL, CM, CK, R, …)
Gx = first chondrite group
Gy = second chondrite group
Ta = first chondrite petrologic type
Tb = second chondrite petrologic type

  • Parentheses
    • Gx(Gy) means a chondrite either of Group X or less likely Group Y. Example: L(LL3)
  • Slash
    • Gx/Gy means a chondrite of either Group X or Group Y. Example: L/LL3
    • One exception is Isheyevo, CH/CBb, where the slash means a chondrite that is transitional between the CH group and the CB group.
  • Dash
    • GxTa-Tb means a chondrite comprised of a breccia whose clasts/components range from petrologic Type A to Type B. Example: CK3-6
    • If A and B are one level apart, then means a chondrite of Type A and Type B. Example: R3-4
    • If the dash comes at the end of the group or type, then what follows provides added information. Examples: -melt breccia, -an, -ung
  • Period
    • Used to denote a chondrite’s petrological subtype and only associated with Type 3 (unequilibrated), Type 2 and presumably Type 1. Example: CO3.0
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Fake Pallasites

These examples go beyond your standard meteorwrongs because they were created for fraudulent reasons. In fact some of these fakes, like Shirokovsky, can even sell as known fakes for more than some real pallasites!

Here is one of the most recent fakes that was submitted to Dr. Carl Agee for classification in summer of 2020.

Fake Pallasite submitted to University of New Mexico. Image Credit: Dr. Carl Agee, 2020

 

 

 

 

 

 

 

Shirokovsky is categorized in the MetBull as a “pseudometeorite“. The write-up is somewhat ambiguous, and should not be. This meteorwrong was man-made with the intent to defraud collectors and institutions. It was sold originally as a fall from Feb. 1, 1956 and many well respected dealers were taken in. What is impressive is that the fraud persisted for a long time before it was properly identified. Now, these are collected as one of the best examples of a fake meteorite.

The “infamous” fake pallasite, Shirokovsky. Image Credit: Mendy Ouzillou
The “infamous” fake pallasite, Shirokovsky (Backlit). Image Credit: Mendy Ouzillou
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Criteria for Classifying Chondrites Based on Petrologic Type

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