Heavy Liquid Separation

This step is the most important in the mineral separtion lab procedure. Heavy mineral separation removes all the minerals that are more or less dense than quartz. Minerals such as rutile (TiO2) and zircon (ZrSiO4) and coal will disrupt later chemistry.

Procedure

Materials:

• 250 ml separatory funnels
• Ring stands
• A solution of lithium heteropolytungstate, LST (PDF): density 2.67 
• Recovery dish
• Recovery flask
• Coffee filters
• Pure water
• Hot plate
• 1L beakers
• Squeeze bottle
• Millipore filtering system

Process:

1. Put a separation funnel in the wire ring over a flask with a ceramic filter funnel. Arrange a coffee filter in the filter funnel to catch the drippings from the separation funnel. Make sure the stopcock of the separation funnel is closed. Pour in enough heavy liquid of the appropriate density to fill the funnel to the "Mexico" mark, or about two-thirds of the way from the stopcock to the widest part of the funnel.
2. Pour ~60 grams of sample material into separatory funnel containing 2.67 density heavy liquid (solution of lithium heteropolytungstates in water, LST), PDF.
3. Let the funnel sit until any grains which are falling through the sediment-free heavy liquid near the bottom of the funnel have settled. This may take fifteen minutes to several hours. The smaller the grain size, the longer this step will take. (Picture 1)
4. Turn the stopcock 90 degrees, so the handle is inline with the discharge spout of the funnel. The heavy minerals will pass through the stopcock and collect on the coffee filter. When draining the heavy minerals, close the stopcock quickly as soon as the heavy minerals are discharged so as not to loose too much LST (PDF). The more liquid there is in the separatory funnel, the easier the minerals separate. Do this several times or until no more heavy minerals settle. 
5. Add 5 drops of water to the heavy liquid and cap tightly. To do this, first rinse off the cap with DI water, use a squirt bottle and squirt water on the cap of the separatory funnel. Let the drops form on the cap, and as they fall off, count and record on the side of the glass funnel (Pictures 2 and 3). Shake the funnel vigorously a few times over a catch basin. Keep a tally on the funnel of how many drops you have added and how many times you shake it. (Pictures 4 and 5)
6. NOTE: Be sure to loosen the cap in the separatory funnel. Failure to loosen the cap after shaking will result in the cap being “glued” in by the dried LST (PDF). In this case, add a few drops of water around the rim of the cap where it touches the separatory funnel. Do not push on the cap or pry on it any way, the funnel may break! Let the water do the job. Only try to twist the cap.
7. Repeat steps 3 and 4 with the 5 drops of water. At this point most of the heavy minerals have fallen out. Add more drops of water 2 or 3 at a time and shake. Drain as necessary. At this point quartz with inclusions will be separated. When the quartz sinks the lighter minerals will float on top of the solution
8. Rinse the coffee filter with pure water and save it, with the heavy minerals. Replace it with another filter.
9. Drain the quartz separate into the clean coffee filter, being careful not to drain the lighter minerals. This step may take several tries. Give the quartz enough time to re-settle before draining more. Rinse the quartz with plenty of water to remove all the LST (PDF). 
10. Place quartz in a clean PP bottle in preparation for ultra sonic leach. Be sure to label the cap and bottle.