Classification of a Chondritic Meteorite Found Near Colgate, North Dakota

Introduction: Meteorites are classified by multiple criteria including; chemistry, mineral structure and mineral abundance. The meteorite studied was found in 1999 in Colgate, ND during a home construction. The main mass of the meteorite weighs 39 Kg making it the largest yet found within North Dakota. The meteorite is a chondritic stone, which is the most common type of meteorite making up 86% of falls [1]. This study determined the class, clan, and the petrological type, which measures the aqueous alteration or metamorphism experienced by the meteorite. Methods: Whole rock geochemical analysis of the meteorite was determined by X-ray Fluorescence, and X-ray Diffraction. The chemical composition of individual mineral grains was determined with a scanning electron microscope and energy dispersive xray spectroscopy. The petrologic structure and optical properties were determined with a polarizing microscope using three thin sections. All equipment used is located either at Leonard Hall, or Upson Bld. 1 at The University of North Dakota. Results: The meteorite has a SiO2/MgO ratio of 1.5, a FeO/SiO2 ratio of 0.71, and a Fe(metallic)/FeO ratio of 0.72. Total metallic Fe is 19.8%, and the olivine Fa (fayalite) composition is 20.27 mol%. The meteorite has good olivine grain homogeneity with less than 5% average deviation. The meteorite’s matrix contains crystalline properties with mostly well segregated chondrules with an average diameter of 0.3mm, and a little igneous glass. With these measurements the meteorite was determined to be H clan meteorite within the ordinary chondrite class, and a petrologic type of 4. Commonly expressed as an H4 Chondrite. Currently the classification is under review by the meteoritical bulletin, and the Colgate Meteorite should be officially added to the bulletin in the coming months