Located at the southern end of the
Awhitu
Peninsula, the Waikato North Head ironsand mine is
approximately 50 km southwest of
Auckland
. The ironsand deposit consists of
Quaternary sands, clays and peats, formed by aeolian and marine processes. We
sampled on widely- and closely-spaced intervals to test variability within the
mining area. X-Ray powder diffraction shows that samples contain feldspars,
quartz, pyroxenes, amphiboles, clays and titanomagnetite. Densities range from
1.6 to 2.5 grams/cubic centimetre, with porosities from 30 to 43 percent. The
percentage of magnetic minerals values range from 0 to 75 percent, slimes (clay
minerals) values of 0 to 26 percent and non-magnetic minerals from 20 to 95
percent. Mineralogical differences in the Mitiwai Formation and Waiuku Blacksand
Member cause bimodal populations in the density, magnetic minerals, nonmagnetic
minerals and slimes plots. The Mitiwai Formation has higher non-magnetic mineral
values and lower density, slimes and magnetic mineral values than the Waiuku
Blacksand Member.