No abstract

Reviews already published on the state of “standard samples” of silicate rocks and minerals, as well as of some samples of other materials that can be used as reference standards for the general analysis of silicate rocks and minerals, have been updated. Usable values of varying degrees of reliability are suggested for major, minor and trace constituents of nearly one hundred different samples. Presentation of the information has been improved with a view to making it more convenient for readers’use.

Because of the disparate data, reported in collaborative analyses of reference samples of rooks, various methods have been proposed for deriving “best values”. This work compares those methods and several additional ones. Included are two simplified estimates of “mode” which yield values close to those of the Dominant Cluster and Gamma Transformation methods. An example is also cited of the hazards that may result from too superficial reading of raw data.

Additional data received since the original report, MRP/MSL 75-132(TR), was prepared, are presented. New recommended values are assigned to several constituents.

Two samples of syenite and one of gabbro were prepared for use as reference material. Analytical data on the composition of the three samples known as SY-2, SY-3 and MRG-1 were reported for more than 100 laboratories from around the world. The analytical methods are described systematically for purposes of comparison, and procedures for deriving assigned values are detailed for both major and minor elements as well as for some of the more common trace elements. Values that are less certain are suggested for less common constituents.