Diamonds in kimberlite apparently reflect physiochemical conditions associated with ancient mantle processes. Chemistries of diamond and of included mineral grains are indicative of crystallization environments (e.g. peridotitic vs. eclogitic affinity), and P-T equilibration values can be calculated from some of these data. Parcels of diamonds from all but two recovery sites in the Colorado-Wyoming State Line Kimberlite District are available for study and a detailed physical and chemical evaluation is proposed. The State Line diamonds constitute the largest and only known comprehensive assemblage of diamonds in North America that represents an entire kimberlite field. Determination of the major physical properties (particularly those related to resorption and deformational processes) of these diamonds will permit evaluation of growth environment(s) and changes that may have occurred during and/or after emplacement of host kimberlite. Supporting information will be derived from diamond chemistry (trace elements and C isotopes) and chemistry of included minerals. These data will be utilized to assess diamond genesis models and petrologic models of the upper mantle under the southern Rocky Mountains. Special attentian will be directed toward the problem of a suggested relationship between eclogitic affinity diamonds and subducted oceanic crust.
