  Microwave energy has been demonstrated to be beneficial for reducing the
energetic cost of several steps of the mining process. Significant literature
has been developed about this topic but few studies are focused on
understanding the interaction between microwaves and minerals at a fundamental
level in order to elucidate the underlying physical processes that control the
observed phenomena. This is ascribed to the complexity of such phenomena,
related to chemical and physical transformations, where electrical, thermal and
mechanical forces play concurrent roles. In this work a new characterization
method for the dielectric properties of mineral samples at microwave
frequencies is presented. The method is based upon the scanning microwave
microscopy technique that enables measurement of the dielectric constant, loss
factor and conductivity with extremely high spatial resolution and accuracy. As
opposed to conventional bulk dielectric techniques, the scanning microwave
microscope can then access and measure the dielectric properties of
micrometer-sized mineral inclusions within a complex structure of natural rock.
In this work a 5 by 20 micrometers size hematite inclusion has been
characterized at a microwave frequency of 3 GHz. Scanning electron
microscopy/energy-dispersive x-ray spectroscopy and confocal micro Raman
spectroscopy were used to determine the structural details and chemical and
elemental composition of mineral sample on similar scale.
