REFLECTIVE SPECTRAL ANALYSIS OF GARNIERITES AS A METHOD OF IDENTIFYING POSSIBLE NICKEL ORE DEPOSITS THROUGH REMOTE SENSING TECHNIQUES

Garnierites are a group of minerals that form as a result of secondary alteration processes creating hydrated, nickel-bearing silicate minerals. Garnierite specimens from New Caledonia consist of a variety of nickel-bearing phyllosilicates such as chrysotile, lizardite, and chlorite. New Caledonia is an island national approximately 1500 km east of Australia. The samples examined were collected from creeks directly downslope of both active and historic nickel mines throughout New Caledonia. The garnierite samples were analyzed to determine if the concentration of nickel in a sample would influence the amount of green wavelength emitted. The green wavelength emission of each sample was measured using an ASD, and the nickel content of the samples was determined using SEM analysis. The data were then compared to one another to determine if there was a correlation between the nickel content of the samples and the wavelength spectra which they emitted. Many of the examined samples lacked any nickel and instead consisted mostly of iron-bearing minerals. Samples which contained sufficient nickel had strong peaks in the range of 500 to 550 nm indicating the reflection of green wavelength while other colors of wavelengths were absorbed. The reflection peaks ranged from 470 to 580 nm through the majority of samples indicating green wavelength is reflected along with part of the yellow and blue wavelengths. Samples dominated by iron-bearing minerals had reflection patterns in the 580 to 650 nm range indicating more yellow, orange, and red wavelengths were reflected. These results suggest that hyperspectral remote sensing may be a viable technique in identifying ore from airborne platforms. Reflective spectroscopy may show some utility in screening or rejecting low value ore for processing for nickel extraction.