Dear Mr. Dembele:

There are only these ways of separation: heavy liquid processing, magnetic

separation, jigging and panning, or flotation. As an alternative, cheap but also toxic is the chemical compound tetrabromoethane (density: 2.97 g/cm³).

With best regards

H.G.Dill

May I recommend

sodium polytungstate (SPT)

Due to its extremely high solubility in water (max. Density to 3.1 g / cm3), it is very suitable as a heavy liquid.

SPT is non-toxic, non-flammable, colorless and in addition it has a solution a very low viscosity.

Best regards,

G. Grundmann

 I agree with Herald. The method also depends on the amount and size of the material to be processed. Larger quantities (several kg) are probably better pre-processed by some type of shaker table. Smaller quantities will do fine with other methods.

Bromoform is ok and I have used it many times. It is primarily classified as an environmental toxin. It can be reused multiple times though. It will be absorbed through skin and by inhalation. By using a fume hood and wearing disposable gloves you should be fine. For post processing acetone is used for washing your separated samples and the glassware. This wash has to be properly disposed.

While tetrabromoethane (TBM) is slightly less expensive than bromoform I find it much more toxic.

There is a new Open File report from the United States Geological Survey prepared by one of my students that deals with separation methods for heavy minerals. https://pubs.er.usgs.gov/publication/ofr20161022

Jaques, I have been in your situation too. I have used simple panning at the site of sample collection (in flowing streams) to get rid of most organic material and some of the quartzofeldspathic grains. The concentration depends on your level of practice! You could also do the panning or tabling (shaker jig) back at the lab. In the lab I have used lithium metatungstate (LMT) which is similar to the LST and SPT products in that it is quite expensive (US$500 per litre) but has the advantages that it is non-toxic and reusable (with care). It has a maximum density of about 3.1 I think but it has to be kept warm and is quite viscous at these maximum values. It can effectively separate the full suite of heavy minerals (>2.9) from quartz and feldspar, but it will not separate very effectively the rarer denser grains like zircon, monazite, rutile from the common Fe-rich ferromagnesian minerals. For this, you may like to investigate micropanning, a physical method, used in some labs doing geochronology separations. However, I have not used this method myself, so can't comment further on it. 

Good luck,

David

thank you all for your input. Actually I want to do provenance study of some sediments: lacustrine and fluvial and in fact I am learning. I don't have a funded project so I have to spend from my savings. If I cannot afford other heavy liquids I will stay with bromoform as it is the cheapest.

Don't forget the river is also separating the heavies as it turns left and right with the heavies piling up on the inner bank. There, you can pan (swirl around water plus sediment) for the heavies in a dish or a shallow plastic pale. It takes practice but it works!

It depends on what minerals you are trying to separate. Normally, a heavy mineral concentrate can be obtained by a wet spiral, gravity-based method (other gravity techniques are tabling and also simple panning as suggested by other replies). This gives a concentrate containing minerals with a broad range of S.G.s. To separate individual components you then need to use a heavy liquid technique which essentially allows you to fine tune your separation. Depending on what you are trying to separate, you may also use other techniques such as magnetic separation (e.g. for ilmenite) or perhaps electrostatic separation.

Mark

can we reuse tetrabromoethane (TBM) during heavy minerals separation experiment?