Northwest Africa 14199 (NWA 14199)

Guelmim, Morocco

Purchased: 2021

Classification: Mesosiderite

History: (F. Kuntz) Three samples were purchased by Fabien Kuntz from a dealer in Guelmim, Morocco in April of 2021.

Physical characteristics: The sample is dark brown and is irregularly shaped, with metal grains protruding through the exterior. The sample has a wind-ablated exterior however, it shows a rollover lip with bubbling on the trailing edge. A small portion of fusion crust is visible in back-scattered electron images. The interior is a breccia of metal grains and silicates.

Petrography: Description and classification (A. Love, App) Sample is recrystallized breccia composed of (vol%): rounded-irregular masses of FeNi metal (50) up to 7 mm and anhedral silicates (50) which show sutured grain boundaries and avg. grain size of 372 µm (n=64). Pyroxenes and plagioclase both show poikiloblastic textures and olivine (<1 vol%) contains well-developed reaction coronas. Additional minerals are: merrillite, ilmenite, chromite, troilite, rutile, schreibersite and both equant and lath shaped silica polymorphs.

Geochemistry: (A. Love, App) Olivine (core Fa₂₇, rim Fa₁₆, Fe/Mn=17.5, n=1); low Ca pyroxene (Fs_32.0±3.8Wo_3.1±0.8, Fe/Mn=23.4±2.9, n=20); high Ca pyroxene (Fs_16.2±1.4Wo_41.1±0.9, Fe/Mn=18.2±1.6, n=11); plagioclase (An_95.2±1.4Or_0.3±0.1, n=8).

Classification: Mesosiderite (estimated class A3). Mesosiderite based on abundance of metal and textures of silicates. Class A based on modal abundance of silicates (32 vol% plagioclase, 61 vol% Opx). Metamorphic type 3 based on recrystallized texture with sutured grain boundaries, absence of fine-grained regions and well-developed reaction coronas around olivine.

Specimens: F. Kuntz holds the main mass. A polished mount and an endcut weighing 15.7 g are on deposit at App.