gravity is low, it should be washed with water in the same manner as described 

 above. 



A rapid and simple method of heavy-mineral separation is described by 

 Wagner and Gableman (1950) and Feo-Codecido (1956). This method in- 

 volves placing the heavy liquid in an evaporating dish, adding the sample, 

 and stirring. The heavy minerals collect at the bottom of the dish and the light 

 minerals float on the surface. The light minerals then are spooned or decanted 

 off, and the heavy minerals are recovered from the bottom, washed, and dried. 

 Although this method is fast, one must be careful to avoid mixing the heavy 

 and light fractions. 



The heavy minerals are usually mounted on glass slides for study. Before 

 the grains are mounted, magnetite is magnetically removed. The slide should 

 contain a representative sample of the mineral grains, and if the sample is too 

 large, it must be split. A micro-split such as described by Otto (1933) is pre- 

 ferred, but if this equipment is not available, the sample may be placed on a 

 paper, coned, and divided into quarters. Alternate quarters are then combined. 

 The process may be repeated until the desired sample size (approximately 1000 

 grains) is obtained. 



Either Canada balsam or Lakeside No. 70 cement may be used in preparing 

 the slide. The writer prefers the cement because it is less difficult to handle. 

 The slide is warmed on a hot plate until the applied cement melts. The melt 

 is stirred with a needle to remove air bubbles. The minerals are sprinkled into 

 the melt, and a cover glass is placed over the minerals. The slide is then 

 removed from the hot plate and the cover glass is pressed down lightly to remove 

 air bubbles and the cement is allowed to cool. Excess cement can be removed by 

 gentle scraping with a knife blade and washing with xylene. After the slide is 

 labeled, preferably by a diamond pencil on the glass, it is ready for examination. 



Mineral Identification 



The mounted minerals are studied with an ordinary petrographic micro- 

 scope. Optical characteristics, cleavage, shape, color, corrosion, and inclusions 

 are the properties evaluated during routine identification. Several references 

 on heavy-mineral identification are recommended, among which are Milner's 

 textbook (1940), Russell's tables (1940-41), Larsen and Burmen (1934), and 

 a section in Krumbein and Pettijohn (1938). The author has found Milner's 

 descriptions and illustrations very helpful, and the arrangement of Russell's 

 tables is very convenient. 



After the minerals have been identified, an estimate of their relative fre- 

 quency is determined. When a large number of samples must be examined 

 rapidly, as in commercial work, a visual estimation of the relative abundance 

 is made. Feo-Codecido (1956) describes the procedure used by an oil company 



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