Hi Paolo,
Remember from my text: "collect around 200 l of alluvial, concentrate by panning, then carefully observe the heavy minerals associations".
I saw some papers telling about 100 kg (the minimal I think). We were more conservative and prudent in some projects.
It is a large quantity; depending on on the pan size, at least 10- 20 pans to wash. Finally, depending on the area, you will obtain some hundreds of grams of heavy minerals; among them, a lot without significance, like magnetite.
And then, in less quantities: pyrope and eclogitic garnet, chrome diopside, picroilmenite, chromite; and, to a lesser extent, olivine . The indicators.
These are the indicators about a kimberlite body. The kimberlite is decomposing fast and will leave this mineral traces in the alluvial, but diluted with other minerals, depending on the distance. It is what you are searching.
Personal (from some sustained field experience, and also a lot of study for Remote Sensing or GIS) I don't think that you can discriminate those minerals, in such small quantities, basis on remote sensing, in alluvials. To few, in order to have a significant spectral signature. See an article, about the kimberlites*
As a good help, starting from the satellite data, you can do a geomorphological analysis. Discriminate well and precise the hydrographic network, then to locate some favorable areas (terraces, dejection cones), for heavy minerals concentration. Among them, beside the indicators, you can find, or not, diamonds (3.52 SG). It is what I done, in my projects. Not Angola, but nearby.
Then, to start exploring, as I wrote before, on the ground. Or direct mining, with the risks of acquiring heavy equipment and be without enough reserves.
I don't know if you have an exclusive license; if yes, can you send me the coordinates, in order to see what it is available (satellite) for that area ?
If you are prospecting, and the area is confidentially, please send something like an nearby area, one-two hundreds kilometers distance.
They are some new satellite data and I want to see the confidence, if you are agreed.
Regards,
Iulian
* http://www.hgimaging.com/PDF/Kruse_IEEE2000_Kimberlites.pdf
"Higher spatial resolution data (1.6m AVIRIS and 4m HyMap acquired in 1998 and 1999, respectively) are being used to map additional detail. Poor exposures, vegetation cover, and weathering, however, make identification of characteristic kimberlite minerals difficult except where exposed by mining. "