CLASSIFICATION OF ORDINARY CHONDRITES

Meteorites are classified by their texture and composition. There are two primary types of textures that meteorites may have. Achondrites come from differentiated bodies. This means that the body they originated from went through a melting process, causing the more dense materials to sink to the center. Chondrites are more primitive. The bodies they originate from are undifferentiated, and relatively unchanged since their formation. Chondrites contain chondrules, small orbs of rocky material suspended in a rocky matrix. In addition to chondrules, chondrites also contain chondrule fragments, metal, sulfides, isolated mineral grains, calcium-iron-rich inclusions (CAIs), lithic clasts (“dark inclusions”), amoeboid olivine aggregates, organics, and pre-solar grains. Chondrites may be split into three classes: carbonaceous, enstatite, and ordinary.

Ordinary chondrites are the most common. Ordinary chondrites could then be further categorized into one of three groups: H (high iron), L (low iron), or LL (low iron, low metal). Assignment of chondrites to a group is based on multiple criteria, such as metal abundance, chondrule abundance, chondrule size, and mineral composition. A complete classification also includes determination of weathering grade and shock stage. The criteria used in classification of chondrites are defined below to provide a framework to compare with our petrographic and geochemical analyses in order to classify the study sample.