Olivine–Low-Ca clinopyroxene, (Ca,Mg,Fe)SiO3, found as a major mineral in eucrites and shergottites. In order to be considered pigeonite, the clinopyroxene must contain 5 to 20 mol % of calcium (Wo5 - 20). Chondrites of petrologic types 4 and below contain significant low-Ca clinopyroxene. During metamorphism to higher temperatures, all existing
Found January 8, 2004
19° 45.4′ N., 54° 56.2′ W. A single complete stone weighing 1,063 g was found in Oman by Mike Farmer. Coincidentally, this An achondrite is a type of stony meteorite whose precursor was of chondritic origin and experienced metamorphic and igneous processes. They have a planetary or differentiated asteroidal origin where the chondritic parent body reached a sufficient size that through heating due to radioactive decay of 26Al (isotope of Aluminum) and Click on Term to Read More was found only ~30 m from an oriented Chondrite meteorites are the most common accounting for 83.6% of falls. Chondrites are comprised mostly of Fe- and Mg-bearing silicate minerals (found in both chondrules and fine grained matrix), free Fe/Ni metal (found in various states like large blebs, small grains and/or even chondrule rims), and various refractory inclusions (such Click on Term to Read More. Analysis and classification was completed at Northern Arizona University (J. Wittke, T. Bunch), and Dhofar 979 was determined to be an olivine–pigeonite ureilite.
Photo courtesy of Mike Farmer—Mike’s Meteorites and Tektites The magnified images shown below, courtesy of John Kashuba, show yellowish, translucent olivines forming 120° triple junctions (left), along with crystals of scarce FeNi-metal between silicate grain boundaries (right). The bottom photo is an excellent petrographic Thin slice or rock, usually 30 µm thick. Thin sections are used to study rocks with a petrographic microscope. micrograph of Dhofar 979, shown courtesy of Peter Marmet.
Photos courtesy of John Kashuba.
click on image for a magnified view
Photo courtesy of Peter Marmet