Octahedrite

Most Common type of iron meteoriteIron meteorites consist mostly of metallic iron alloyed with typically between ~5 to ~30 wt% nickel. The main metal phases are kamacite α-(Fe, Ni) and taenite y-(Fe, Ni). Based on their group classification, they may also contain a small weight percentage of one or more of the following minerals: • Click on Term to Read More, composed mainly of taeniteLess common than kamacite, both taenite and kamacite are Ni-Fe alloys found in iron meteorites. Taenite, γ-(Fe,Ni), has 27-65 wt% Ni, and forms small crystals that appear as highly reflecting thin ribbons on the etched surface of a meteorite; the name derives from the Greek word for "ribbon." Click on Term to Read More and kamaciteMore common than taenite, both taenite and kamacite are Ni-Fe alloys found in iron meteorites. Kamacite, α-(Fe,Ni), contains 4-7.5 wt% Ni, and forms large body-centered cubic crystals that appear like broad bands or beam-like structures on the etched surface of a meteorite; its name is derived from the Greek word Click on Term to Read More and named for the octahedral (eight-sided) shape of the kamacite crystals. When sliced, polished and etched with an acid such as nitric acid, they display a characteristic Widmanstätten patternCharacteristic cross-hatched pattern visible on the surface of octahedrites, pallasites and even large metal blebs in chondrite melts and mesosiderite nodules after polishing and etching with an acid solution like nital (nitric acid in solution with ethanol). The acid will preferentially etch the iron based on its nickel content - Click on Term to Read More. Spaces between larger kamacite and taenite plates are often filled by a fine-grained mixture of kamacite and taenite called plessiteA fine-grained intergrowth of kamacite and taenite that fills in the wedges between wide kamacite and taenite bands in octahedrites. The name derives from the Greek word for "filling." Click on Term to Read More. Octahedrites are divided into several groups based on the width of their kamacite lamellae, and each subgroup is associated with a particular chemical class of iron meteorites. An etched slice of the IVA iron meteoriteWork in progress. A solid natural object reaching a planet’s surface from interplanetary space. Solid portion of a meteoroid that survives its fall to Earth, or some other body. Meteorites are classified as stony meteorites, iron meteorites, and stony-iron meteorites. These groups are further divided according to their mineralogy and Click on Term to Read More Gibeon is shown below.