standby for northwest africa 4156 photo
Purchased before 2006
no coordinates recorded

Five paired stones having a combined weight of 711.6 g were found in Northwest Africa and sold in Erfoud, Morocco to meteorite collector C. Anger of Austromet. Samples of each stone were submitted for analysis and classification to the Museum für Naturkunde (A. Greshake and M. Kurz), and a NWA-series designation of 4152 through 4156 was assigned to the members of the pairing group. Northwest Africa 4152–4156 was determined to have anomalous silicate ranges; the average Fa value of 20.4 is consistent with the H chondrite group, while the average Fs value of 20.4 is consistent with the L chondrite group. Therefore, it was determined that this pairing group belongs to the transitional H/L chondrite group.

The H/L chondrite group comprises a couple of dozen members, of which some or all might represent a distinct ordinary chondrite parent body. Northwest Africa 4152–4156 is either a representative of this distinct parent body, or alternatively, the anomalous silicate values may indicate that the Fa and Fs ranges for the H and/or L chondrite groups need to be extended. The potential identification of further chemical and petrographic characteristics inconsistent with the known H and L chondrites would help provide a definitive assignment.

ordinary chondrite Fa and Fs ranges
  Fa Fs
H 16–20.4 14.5–18.1
H/L 19.5–21.8 17.2–21.2
L 22–26 18.7–22
L/LL 25.5–26.5
LL 26–33 22–26
H/L chondrite ranges derived from published values for equilibrated H/L members.

The petrographic features of this meteorite were determined to be consistent with type 6, which is a very rare type for this transitional group shared by only three other members: DaG 591, SaU 324, and NWA 4150, the latter being a melt rock. The five meteorites composing the 4152–4156 pairing group have shock stages in the range of S3–S4 and weathering grades in the range of W2–W4. The photo shown above is a 3.31 g partial slice acquired from Christian Anger which was cut from the 165 g NWA 4156 stone. Thank you dearly departed friend.