Most processes rely on density differences to separate light minerals from heavier ones, so the ore is crushed and ground to release the ore minerals from the gangue.
In the case of Mountain Pass bastnasite, a hot froth flotation process is used to remove the heavier products, barite (BaSO4) and celestite (SrSO4), by letting them settle out while the bastnasite and other light minerals are floated off.
However, the light minerals quartz, chlorite, micas, and secondary clay minerals dominate the soil mineral composition.
These rocks are generally medium- to coarse-grained and are foliated due to the alternate arrangements of minerals and the dimensional orientation of light minerals such as quartz and feldspar (Balakrishnan et al. 1990).
Selective percussion drilling within the sinkholes provided vibra-cores for mineralogical and sedimentological investigations (grain size distribution, heavy- and light minerals, X-ray diffraction, thin sections) as well as AMS 14C dates.
The current investigation involved the study of grain-related parameters such as morphology, grain size and accessory minerals in gold aggregates in context with a detailed analysis of heavy and light minerals as well as heavy artifacts in the mineral assemblage of the placer deposits.
