Heavy Mineral SamplingNice to read the entire article: Diamond geology by DeBeers group
https://www.geokniga.org/bookfiles/geokniga-diamondgeology.pdf
But read page 9 on 3. Heavy Mineral Sampling
Indicator mineral techniques used in exploration for primary deposits are based upon
the preservation of certain kimberlitic mineral species in the secondary environment,
and studies of the upper mantle from where these minerals originate.
“Heavy minerals” are a select group characterised by their high specific gravity
(generally greater than quartz at 2.67). Most are resistant in the secondary
environment and many are oxides. The important heavy minerals in kimberlite
exploration are mantle-derived xenocrysts of pyrope garnet, picro-ilmenite, chromian
spinel (chromite), chrome diopside (a variety of clinopyroxene) and of course
diamond. In cold climates, where chemical weathering of minerals occurs at a much
slower rate (e.g. in Canada), olivine may also be important.
These minerals are released into the secondary environment by weathering and erosion of a kimberlite intrusion, whilst the bulk of the kimberlite rock (comprising largely olivine, and
serpentine) weathers to clay minerals which are easily transported away by wind and
water. The presence of these indicator minerals in soil and stream samples points to
the local presence of their source kimberlites.
An important point to note is that the presence of diamonds alone in such samples may be a red herring, since diamonds are so extremely resistant in the secondary environment, that they may survive several sedimentary cycles and occur in concentration far from their primary source.
PS Read the last news release about Middlepits Project, Botswana attentively!!!!!!
GLTA Raypar