have highly variable stabilities with respect to transport/weathering but the combined effects of chemical weathering, transport and diagenesistend to decrease their percentage in the whole rock. Therefore, the average heavy mineral yield in sandstones is about 1% but can be a lot lower in old/recycled sandstones. The individual properties of heavy minerals being very different from one another and their relative abundance being a direct proxy of the nature of the source terranes and transport/recycling mechanism, heavy minerals have been used since the 19th century as a provenance tool.
History
The first published provenance analysis is often considered to be the study of the Dutch-Coast sand dunes by J.W. Retgers who combined petrography, chemical signatures of opaque minerals and single grainchemical analysis to assess provenance patterns in the basin. This study was followed a year later by the complementary investigations of J.L.C Schroeder Van Der Kolk who used heavy minerals to study the provenance of Quaternary sandstones of “alluvial or diluvial” origins.
Separation
Heavy minerals are often extracted from large samples as they represent a very limited fraction of old and weathered sandstones. Common procedure involves :
crushing with a jaw-Crusher/mill. To limit the amount of broken grains, the crushing is usually conducted in a "step-by-step" way in the jaw crusher
The crushing product is then usually sieved at 500, 250 or 125 μm. In most of the original heavy minerals analysis, the 125-64 μm fraction is retained for the separation work as it gives a representative yield of the heavy minerals, makes the mounting easier and allows a more detailed petrographic identification.
The samples are then repeatedly washed with water and left for decantation to remove the clay fraction
acid etching to eliminate potential carbonate cements and ferruginous coatings is also common. Preparation uses a low concentration acetic acid, as more concentrated acids or hydrochloric acid may introduce a bias in the heavy mineral content by dissolving the most fragile phases such as apatite or calcic amphibole. If this technique is used, the sample is then boiled with distilled water and dried in an oven.
