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Roll Overs:
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Copyright (c) Scott McGregor.
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2.4 gram slice, approximately 25 x 20 x 2 mm. CO3
TKW 160 grams. Fall not observed. Purchased December 2021 from a dealer in Purchased by Shun-Chung Yang and Juan Chen in 2021 from a dealer in Tindouf, Algeria.
  
Scott writes:
Image 3 is from Tony Irving, the official classifier. It was sent to me by Shun-Chung Yang who wrote:
There is the image for SCY-59, the NWA 14995. I have no ability to say it’s a CO3 based on it. But it seems a strong support for Tony!
From Metbull:
History: Purchased by Shun-Chung Yang and Juan Chen in 2021 from a dealer in Tindouf, Algeria.
Petrography: (A. Irving, UWS and J. Boesenberg, BrownU) Well-formed unequilibrated, glass-bearing chondrules (exhibiting a wide range in apparent diameter of 430±320 µm, N = 26), together with small, zoned olivine fragments and rare very small, very fine-grained CAI, are set in a fine grained matrix (~ 40 vol.%, deep reddish-brown in thin section) containing magnetite, troilite, pentlandite and kamacite.
Geochemistry: Olivine (Fa14.7±8.6, range Fa0.4-39.7, N = 17; Cr2O3 in ferroan olivine 0.01-0.48 wt.%, mean 0.15±0.11 wt.%, N = 13), low-Ca pyroxene (Fs15.4±9.6Wo1.9±1.4, range Fs1.0-29.5Wo1.0-5.0, N = 8), augite (Fs6.2Wo36.7; Fs4.1Wo41.4; N = 2).
Classification: Carbonaceous chondrite (CO3, magnetite-bearing).
I know, yet another NWA, but this one is actually interesting! I received it as a (very nice) gift from Shun-Chung Yang, who tells me he was surprised it turned out to be a CO3, given the large chondrule size. Maybe the beauty among the CO3’s? Most of them are pretty drab…
Pictures may be used with attribution. |
Click to view larger photos
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Found at the arrow (green or red) on the map below
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John Divelbiss
8/23/2022 6:35:15 PM |
Technical averages and criteria tend to change over time with more information and/or analysis...maybe the CO type, and other C's are some of the most varying tracks to follow? |
Scott McGregor
8/23/2022 1:17:45 PM |
From an email exchange with Shun and Tony Irving (classifier), Tony does not think there is any doubt about SCY-59 (NWA 14995) being a CO3 chondrite. He tried to make the case for an anomalous CO3 because of the presence of magnetite instead of metal, but the reviewers pointed out that some CO3 chondrites contain both magnetite and metal (based on work by Alan Rubin). I've asked Paul if he can post an additional BSE image from Tony supporting the classification. |
Jason Utas
8/23/2022 11:14:29 AM |
Matrix and chondrules look carbonaceous. Doesn*t fit criteria for a CO, so should probably be anomalous or ungrouped.
*Does chondrule diameter no longer matter for classifications? With unequilibrated chondrites where Fa/Fs ranges are large and averages don*t mean much, I don*t see how or why a rock that*s petrographically not a CO would be classified as a CO. |
Scott McGregor
8/23/2022 10:25:53 AM |
Mendy, are you thinking CK3 or CV3? The tiny CAI seem off though... |
Mendy M Ouzillou
8/23/2022 8:44:32 AM |
I, like Bernd, find it highly unlikely that the classification is correct. The mean chondrule diameter is far too large for it to be a CO3, but the finding of small CAI compared to OC makes this unlikely to be an L or LL chondrite. I think this meteorite deserved more testing including Oxygen isotope analysis. |
Bernd Pauli
8/23/2022 5:17:56 AM |
Hmm... Looks more like an L or an LL chondrite! |
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