by panning before the separation is made. In general, the older the geologic age 

 of the rock, the fewer the heavy minerals. 



The funnels are set up as shown in Figure 6-4. The pinch clamp on the 

 upper funnel is closed and the funnel filled about two thirds full of a heavy 

 liquid. The most commonly used heavy liquids are bromoform (sp. gr. 2.86) 

 and acetylene tetrabromide (sp. gr. 2.96). Both are soluble in alcohol, color- 

 less when fresh, nonpoisonous, and essentially chemically inert. The fumes of 

 both are not unduly disagreeable but are sufficiently toxic to require adequate 

 ventilation. A large cover glass placed over the funnel containing the heavy 

 liquid minimizes evaporation. The writer prefers acetylene tetrabromide because 

 a cleaner mineral separation generally is obtained; however, the odor is slightly 

 more objectionable than that of bromoform, and acetylene tetrabromide passes 

 through filter paper more slowly. 



The sample is placed in the heavy liquid in the upper funnel and stirred 

 gently. Minerals having a specific gravity greater than that of the liquid will 

 sink and be retained by the pinch clamp. The heavy minerals may adhere to 

 the side of the funnel just above the stem, but they can be dislodged by gentle 

 stirring with a glass rod. When the heavies have settled, a filter paper is placed 

 in the lower funnel, the pinch clamp is opened momentarily, and the minerals 

 are flushed on the filter paper. If the sample contains many heavy minerals, it may 

 be necessary to repeat the operation two or three times to prevent clogging of 

 the funnel stem and rubber tube. After the heavy liquid containing the minerals 

 is allowed to filter off, the filter paper is removed to another funnel, and the 

 minerals are washed with alcohol. The heavy minerals are allowed to dry and 

 then are transferred to a small glass vial. Another filter paper is then placed in 

 the lower funnel, the pinch clamp is opened, and the heavy liquid and the 

 remaining light minerals are drained off. The liquid is saved and can be reused. 

 The light minerals are washed with alcohol, dried, and filed for further study. 



The alcohol washings are placed in a collecting jar, and the bromoform or 

 acetylene tetrabromide is reclaimed by water washing. When the jar is about 

 half full of alcohol washings, an equal volume of water is added, and the jar is 

 shaken vigorously. Alcohol, being soluble in water, is separated from the heavy 

 liquid, which settles to the bottom. The alcohol-water solution is decanted off, 

 and the process is repeated three or four times in order to remove excess alcohol. 

 After the final decantation, the heavy liquid and remaining water are placed in 

 a separatory funnel. The heavy liquid is drawn off and passed through several 

 filter papers, which absorb included water and remove other suspended solid 

 matter. The liquid may then be reused, but it should first be tested either by 

 a hydrometer such as described by Tester (1931) or by a mineral of known 

 specific gravity (quartz, calcite, dolomite, anhydrite). Commercial bromoform 

 is often diluted with alcohol and should be tested before using. If the specific 



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