Hammadah al Hamra 337              29°00′00′′N, 12°07′40′′E

Hammadah al Hamra region, Libya

Find: 24 February 2001

Carbonaceous chondrite (CK4)

History: A single stone weighing 198 g was found in February 2001 in the Hammadah al Hamra region of Libya by Giovanni Pratesi (MSP) during a scientific expedition.

Physical Characteristics: (V. Moggi-Cecchi, A. Salvadori, and G. Pratesi, MSP) The main mass has a dark brown external surface with fusion crust in some areas. In hand sample the chondrules are set in a dark green matrix and CAIs (up to 1 mm) are present.

Petrography: The thin section contains few chondrules (not perfectly delineated and sometimes altered) set in fine-grained matrix with several coarser-grained olivine crystals. Chondrules range from 380 to 1800 µm (mean value 700 µm on n = 25) and account for about 20% of the total volume. Chondrule textural types: POP = 72%, PO = 12%, and GOP = 16% (all vol%). Very rare and extremely altered AOIs (2 vol%) and abundant CAIs (~1 mm) are observed. Plagioclase crystals can be found in GO and PO chondrules. Metal alloys are extremely rare (<0.01 vol%). Magnetite (inside and outside chondrules) is abundant (~8 vol%). Sulfides (mainly pyrrhotite) are rare and are located in the matrix. Rare kamacite and moncheite (Pt,Pd)(Te,Bi)₂ are also present.

Chemistry: (EPMA) Olivine compositions are quite homogeneous (Fo_68–75; mean Fo₇₄), with the exception of rare zoned olivine crystals (Fo_68–93) in PO chondrules. Low-Ca pyroxenes in GOP chondrules are En_90-100. High-Ca pyroxenes in POP chondrules have an augitic composition (Wo₅₀En_50–60Fs_0–10). Plagioclase and devitrified mesostasis is albitic (An_25–50). Magnetite (Cr₂O₃ = 2–3 wt%): Sulfides (Ni = 1–2 wt%); kamacite with low Ni.
Oxygen isotope: (I. Franchi, R. Greenwood, OU) δ¹⁷O = −3.668, δ¹⁸O = −0.369, ∆¹⁷O = −3.496 (all ‰).

Classification: Carbonaceous chondrite (CK4); S1, moderate to extensive weathering.

Specimens: The main mass (174 g), a 24 g type specimen, and two thin sections are on deposit at MSP (inventory number MSP 1592).