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Sampling and Processing Details

Since 1994, the Geological Survey of Finland (GTK) has been providing customized, high quality diamond exploration services with complete confidentiality to companies both within Finland and abroad. We specialize in laboratory services and exploration techniques from regional through to prospect scales. To date we have taken and processed nearly 30,000 quaternary samples for diamond exploration companies.

The GTK Research Laboratory has developed high recovery separation techniques for kimberlite and diamond indicator minerals, including preconcentration by GTK modified Knelson concentrators (3" and 4.5"), heavy medium removal of light minerals and dry magnetic separation of magnetite from the heavy fraction. The technique allows rapid and routine processing of reconnaissance and regional scale exploration samples, maintaining a constant 90% recovery rate for the critical pyrope garnet, picroilmenite and clinopyroxene grains in the 0.25 to 0.50 mm grain size range.

We offer the following laboratory scale processing services for Quaternary samples. The unit weight of samples to be processed by a 3” Knelson concentrator is 15 kg of material finer than 1 mm (or 2 mm). For a 4.5” concentrator the corresponding weight can vary between 30 and 45 kg. The processing includes:

• Removal of material coarser than 1 mm (or 2 mm) by wet sieving.
• For till samples rich in magnetite, low intensity wet magnetic separation of magnetite.
• Modified Knelson preconcentration through pre-concentration in a dedicated facility at GTK Outokumpu.
• Dry magnetic separation of magnetite.
• Dry sieving separation of the 0.25 – 0.50 mm and 0.50 – 1 mm (or 2 mm) fractions.
• Heavy liquid separation (methylene iodide, d = 3.3 or less if required) of the 0.25 – 0.50 mm and 0.50 – 1 mm (or 2 mm) fractions.
• Microscope observation services conducted by highly experienced skilled pickers are also available.

Or if no preconcentration is needed, we can also start straight from preconcentrates provided by the client. The heavy medium separations and mineral analyses (microprobe and SEM) are done at the GTK laboratories in Espoo, near the city of Helsinki.

We can also provide state of the art services for tailor-made heavy mineral studies exploiting the -0.25mm fraction from a quaternary sample. The heavy mineral concentrate is mounted and scanned automatically by SEM to locate and identify various indicator minerals species. This enables recovery of indicator minerals that are tedious or even impossible to observe under binocular microscope e.g. minerals derived from PGE-mineralization or alkaline source rocks.