MIAC

Iron and Stony-iron Meteorites

Iron Meteorites

Annaheim

This meteorite was found in 1916 about 10 km north of Annaheim, a settlement somewhat about 100 km east of Saskatoon. It was discovered by Mr. William Huiras who was mowing hay on his farm. It is believed to be related to a spectacular fireball observed some two years earlier. It is a crescent shaped medium octahedrite, with a mass of nearly 12 kg and showing very clearly the dimpling or 'thumb-printing' of the surface which is often found on iron meteorites. The main mass is currently held in the Canadian National Meteorite Collection, Ottawa (Ref. R.A.A. Johnston & H.V. Ellsworth (1921): Trans. Roy. Soc. Canada., Sect. IV, p. 92.) (Photo courtesy Geological Survey of Canada)



Casas Grandes

This meteorite from Chihuahua, Mexico is a medium octahedrite with an original mass of 1547 kg. It is particularly interesting because it was found in an ancient tomb. Further details can be found in Buchwald's Handbook of Iron Meteorites. The slide shows a polished slab cut from the main mass, which has been etched to reveal the intricate intergrowth of oriented kamacite bands known as the 'Widmanstätten structure'. The bands are oriented along the (III) (octahedral) planes of the original metal which had the FCC taenite structure. Hence the name 'octahedrites'. Medium octahedrites have kamacite band widths from 0.5-1.3 mm. (Photo courtesy Geological Survey of Canada)



Stony-Iron Meteorites

Springwater.

Three masses (38.6 kg, 18.6 and 10.6 kg) of this stony iron pallasite were found near the Saskatchewan town of Springwater (120 km west of Saskatoon) in 1931. The meteorite is made up of 1/3 metal (kamacite and taenite) and 2/3 olivine with minor amounts of other minerals, including the rare phosphate minerals farringtonite (Mg3(PO4)2) and stanfieldite (Ca4(Mg,Fe)5(PO4)6) and the more common phosphate - merrillite (= whitlockite, Ca3(PO4)2). Even some of the olivine is P-rich. Only 35 pallasites are known and thus they are rather rare meteorites. They are also particularly attractive as can be seen in this slide of a polished slab. (Photo courtesy Geological Survey of Canada)



MIAC Slide Group and Michael Higgins