Magnetic separation using a properly calibrated Frantz should work (probably even a STRONG magnet would play the trick)

We routinely face this issue in our lab. Frantz is difficult since the majority of pyrite is non-magnetic @ 1.7amps. A density separation is not really possible since they are both > 4.7 (there are no easy-to-handle heavy liquids that dense).

I know you said you don't want to use any chemical treatment, but concentrated nitric acid is by far the easiest and quickest way to remove pyrite from zircon. It takes

May I suggest a separation method with absolutely no chemicals, I have applied for the picking of apatite and zircon (for fission track dating).

My apatite concentrates were purified by hand picking under the stereo microscope. You do this with the following devices:

- Hand-picking frame, pattern 1 cm width (attached photo - left)

- Hand-picking apparatus (attached photo - right) in which the air is drawn through a transparent tube by means of a small aquarium air-pump.

At the top there is a replaceable fine metal tube whose diameter can be freely selected. The small hole in the Plexiglas tube can be opened or closed with a fingertip. The pyrite and other impurities are collected in the tube, the zircons stay on the hand picking frame are and can then be enriched arbitrarily.

Try it, it works!

Hello Zehra,

You didn't say how fine the sediment is and how much separate is needed. For dating purpose Guenter's suggestion is perfect. The only problem is, if you have very rare and small grains of zircon in sediment. Then I would suggest to make heavy liquid - bromoform separation first and to apply hand-picking only on obtained small quantity of heavy fraction (separating zircon from pyrite and the rest heavy minerals). I don't know what kind of equipment you have, but basic separation of heavy fraction can also be done by aero-cyclone,hydro-cyclone, centrifuge e.t.c. In all cases final purifying of concentrate is necessary. 

Dear Dr. Deveci,

the hot issues in this mineral processing project have already been touched. It is the grain size of the heavy minerals in question and their quantity relative to the matrix. On the other hand, the degree of purity you want to achieve is another question you have to answer yourself. If you can avail yourself of a large quantity of material, even at a small grain size you can embark on a semi-industrial processing, the methods of which have already been mentioned by Dr. Trajanova. If you are short of sample material you cannot avoid of using one of the common heavy liquids to get rid of the matrix, or in other words of the rock-forming minerals. As you deal with sedimentary rock, this should not be a problem to be solved, because sodium poly-wolframate is easy to handle and non-toxic. If the grain size is appropriate for a manual sorting by eye, separation under the stereomicroscope is the method of choice due to the striking metallic luster of the Fe sulfide. If the material is very fine-grained, what is often the case in sediments you should test the vulnerability of pyrite to attrition and oxidation, which increase with the complexity of its morphology and the decrease in grain size. Mild mechanical attrition combined with mild oxidants lead to a swift comminution and you might do better away this trash mineral. The opposite direction of heating up pyrite might be useful in some cases to increase the magnetic characteristics, but the effect on this point is hard to predict. There is no standard procedure that works with this couple of minerals. You must know more about the compositional and physical features of your minerals under consideration.

Best regards

H.G.Dill

Hello,

My advice would be similar to those previously given: magnetism first, then a succession of heavy liquid (modified bromoform with acetone, to fit the requested density), and finally handpicking (depending on the size of the residues fraction).

Or with some luck, a "more stupid" way: vibrations and vanning!

Courage and good luck,

Bruno

Hi Zehra,

You might like to try the following technique. I don't have a reference for this, as it was passed on to me by someone else. I have used it and it works very well!

In order to recover zircon minerals from a heavy mineral concentrate, a series of gravity and magnetic methods are used. Pyrite, (when present in the sample) has the same physical properties as zircon and, when abundant, the pyrite can create difficulties when trying to isolate and mount these zircons. Below is a technique that floats off the pyrite leaving behind its more desirable heavy silicates.

 Materials:

1% solution K-amyl-xanthate

1% solution of KOH

Clean 200-250mL glass beaker (or larger, depending on sample size)

10mL graduated cylinder

Ultrasonic bath

Water dispensing bottle with a fine tip

Filter paper

Method:

1-Pour the sample into a clean beaker.

2-Add 50mL of cold deionised water.

3-Add 3-5mL of 1% K-amyl-xanthate solution.

4-Add 2-3 drops of 1% KOH solution to adjust pH.

5-Place beaker into ultrasonic bath for about 5 minutes, stirring occasionally (swirling will do)

Note: Turn bath off when swirling. Do not touch beaker while ultrasonic bath is on and do not place beaker directly on tank bottom. Use clamp to hold beaker to the side.

6-Carefully decant the supernatant solution into a funnel lined with a filter paper.

7-Using the fine tipped water bottle, gently spray the sample with a small amount of water. The pyrite will float.

8-Decant the pyrite into a new funnel lined with a filter paper.

9-Repeat steps 7 and 8 until all visible pyrite is gone. If there is very little zircon in the samples, I would suggest leaving some of the pyrite behind to be sure that none of the zircon is lost. 

Tip: If sample is larger, you can double or triple the quantities.

 The K-amyl-X solution has a shelf life. It will become noticeable that the pyrite will no longer float so readily when the solution has been sitting around for a year or more. Therefore, a fresh solution of K-amyl-X will have to be made.

 This method is applied to samples that are approximately 1g or bigger. If sample is smaller than 1g the pyrite may be burned off by placing sample in a solution of 4N HNO3.

You can hand pick it, float it, or dissolve it.  The latter is routinely done with concentrated hot nitric acid (aqua regia), which we routinely do in our lab.  See the web for technique and approach.  It takes maybe 30 minutes, and should be done in a hood.

Why you avoid chemicals?? It is easy to remove pyrite chemically!!!

Yes I know how it is easy by chemicals but some cases, chemicals may destruct zircon. I would like to avoid it. 

Yes, the chemical treatment may present a problem.  If the zircons have high damage the notable methods of chemical separation may cause dissolution of grains (or high-damage parts of grains).  Zehra, it has been a year, can you give us an update?

Sure, John. Actually I tried physical method how Guenter Grundmann explained but it didn't work or maybe I couldn't do that. what I am doing is If zircons are seen not to damaged under microscope, I use chemicals, nitric acid for dissolving pyrite. But If zircons look damaged or if they are metamorphic, I use Frantz in 1.7 A  which pyrite is non-magnetic and some zircon grains are magnetic. But it is still possible to find zircons on pyrite fraction and I pick zircons by doing some small vibrations on picking plate. Pyrites are heavier than zircons and when I vibrate the picking plate, pyrites accumulate in the outer circular zone, toward the center, zircons are located. It works, but not totally effective, of course. 

 Dear Zehra,

I understand that the separation of minerals is not the most important of your business.

The simplest method of separation - manual separation of minerals during irradiation with UV radiation. Zircon will luminesce green-yellow light color (see answers to Petra Vesela). Pyrite is not luminescent.

If you have a lot of minerals, I recommend using the automatic X-ray luminescent separators, which are used for diamond industry. In the diamond industry zircon is a poor mineral which is extracted together with diamond and clogs concentrate.

But if you do not afraid some change the characteristics of zircon, it is possible to heat a mixture of pyrite + zircon at 200 -300C for 10 - 15 minutes. After that, zircon becomes lighter, but they restore color later. The pyrite becomes magnetic. After the procedures ferropirite is removed by magnetic fild.

Vasily