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INTRODUCTION

A single unusual vesicular material having an approximate recoverable mass of 3.5 kg was unearthed in a field near the town of Granada, Colorado (fig. 1). The material is composed of ultrarefractory and high-temperature derived mineral phases such as calcium silicates (fig. 2). Moreover, the material is enriched in refractory trace elements, rare earth elements (REE), and elevated oxygen isotopes of 18O and 17O. No terrestrial or extraterrestrial material exactly matches the composition of the Granada material, with the exception of a localized witnessed fall near Madrid, Spain. Two hypotheses exist in regards to the origin of the Granada material. The first hypothesis is that the material is an unique refractory calcium aluminum inclusion (CAI), which is typically 1.0 cm in diameter, found as spherical inclusions in chondrites. Boss (1995) proposed that CAIs had to have been initially larger before being broken apart 10 million years after the formation of the solar system, in order to be incorporated into chondritic bodies. The second proposed hypothesis is that the material is steel slag, an industrial byproduct. The material has a bulk chemistry resembling that of steel slag. However, free calcium oxide, which is always present in steel slag, is absent in the Granada material.

This study focuses on the geochemistry and mineralogy in an attempt to ascertain an origin of the Granada material. Mineral phases are identified using both qualitative and quantitative procedures such as electron microprobe analysis Moreover, mineralogy and spectroscopic reflectance are compared to other asteroidal bodies using very near infrared spectroscopy (VNIR).


Figure 1. Location of study site near Granada, Colorado.


Figure 2. Slab section of the Granada ultrarefractory material.