In 1979, Masuda and Ikeuchi found out a type of lanthanide tetrad effect in seawaters and phosphorite.At the time of this finding, it was logically reasoned that there should be another type of lanthanide tetrad effect which stands in conjugate relationship with the type as found for seawaters. This paper reports our success in evincing the previous reasoning about the bilateral appearances of the lanthanide tetrad effect, i.e., empirically disclosing the conjugate aspects of the effect in question. Thus, there are two types of tetrad effects for lanthanides in nature, which will be called W and M types for convenience sake according to their apparent shapes. The W tetrad effect is observed in the natural waters and related materials. This suggests that an M tetrad effect can be observed in the solid pro ducts probably having remained after leaching by aqueous medium, in which the W tetrad effect can be operative. Besides, the M tetrad effect have been found in an experiment concerning the lanthanide partitioning between CaSO4 and H20. For the geological rock specimen, a remarkable M tetrad effect is recognized for the leucogranite from South China.To a lesser extent, a similar effect is found in a siliceous ore from the kuroko area.

No abstract