Element concentrations in percentS:

Objective and detailed data arc necessary:for app!ication of garnet-ratlo studies to till provenance. The garnets in common use differ sigrtificantly in cell dimensmn. Ratios of purple-colorless/orange-red garnets have been used empirically to establish prove-nance of tills in eastern North America. (See I)reimanis and others, 1957; Dreimanis, 1960; Connally, 1964.) Garnets are common in Pre-cambrian rocks, and, because they are chemically and mechanically resistant minerals, they are relatively abundant in heavy-mineral fractions of tills in Quebec, Ontario, and New York. This, plus the ease with which they are identi-fied, makes them attractive as potential indica-tor minerals. Some dangers inherent in broad regional con-elusions based on garnet colors in a population with relatively low sample density are: (1) ~ Manuscript received December 11, 1967. small local sources of garnet could mask any re-gional trend in the ratios; (2) glaciers could lo-cally incorporate garnets from older glacial sed-iments having different provenance; (3) com-monly in areas with a complex ice-flow history, only detailed local work can indicate which till unit happens to show in a given surface expo-sure; and (4) it is possible that several combi-nations in the complicated solid-solution garnet series could produce the same general color. In addition, color has been treated as a subjective criterion which makes difficult the comparison of results of different workers. For example, both color-classes of garnets are present in tills of the Appalachian region, Que-bec. (See Dreimanis, 1960, p. 112.) The present TABLE 1.--Pr0perties of orange-red and light purple garnets ~ ~ G a r n e t ~ color Orange-red Light purpl