US gun massacres are preventable
I am not quite as despondent as Kamerow about the aftermath of the US school shooting on Valentine’s day,1 but I am angry about what has been allowed to happen.

Only a few US households (probably one in three) possess guns, and just over …
Yet another US massacre with a semi-automatic rifle
Can outraged Florida students move us to action this time?
Limitations on the interpretation of biotite substitutions from chemical analyses of natural samples
Biotites, as well as other phases, are sufficiently complex chemically that there are numerous sets of linearly independent exchange components with which to describe the composition of a naturally occurring crystal. Even after complete chemical analysis, this leads to ambiguities in the correlation of exchange components with valid substitution mechanisms in complex phases. The best means of identifuing valid substitutions are by the observation of simple endmember compositions, the investigation of compositional changes in zoned crystals or petrogenetic sequences, and by direct experimental synthesis.