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Europium (Eu)-rich dark monazite has been found in 64 alluvial concentrates from 14 areas across Alaska between the Canadian border and the west end of the Seward Peninsula. This monazite is characterized by gray to black color, pelletlike form, high-Eu and low-thorium (Th) contents, turbidity caused by microscopic clouds of amorphous carbon and sagenitic rutile rods, and many inclusions of siltsized detrital minerals. Density (D) of Alaskan dark monazite ranges from 4.25 to 4.70, mainly due to the presence of inclusions. Otherwise, physical properties are similar to those of yellow mona zite. Refractive indices, a and 7, are similar to those of yellow mona zite, but interference figures are generally diffuse and show small (0°-5°) positive 2V. X-ray diffraction patterns and cell parameters are similar to those of yellow monazites. The average composition of 11 dark monazites from Alaska is (in percent): La-jOs 13.54,

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A visual comparison method for semiquantitative spectrographic analysis of plant ash by dc arc technique has been applied to a wide variety of plant material. A split slit technique utilizing a Hartmann diaphragm and step filter assemblage enables the simultaneous recording of volatile elements from a short burn at 100% transmission and less volatile elements from a total energy burn at 15% transmission from the same electrode charge. Volatile elements, e.g., Ag, As, Bi, etc., are thus detected at low concentrations without the necessity of a separate analysis. Standards in a plant ash base are prepared in progressively lower concentrations from spectrographically pure powders in ranges applicable to most plants. Results are reported as six possible logarithmically spaced intervals per order of magnitude. Results show the repeatability to be within one reporting interval of the standards at the 68% confidence level and within two reporting intervals of the standards at the 95% confidence level. The over-all speed of the method suggests an application to large numbers of samples, and the analysis of more than 800 samples per man-month attests to the value of this method in reconnaissance studies.