Which statement best describes Bowen's Reaction Series?

• A. Olivine is among the last minerals to crystallize
• B. Olivine is among the first minerals to crystallize
• C. Quartz crystallizes before olivine
• D. Feldspars crystallize before olivine

Answer: (B)

As magma cools, minerals crystallize in a predictable order based on their stability at decreasing temperatures. The highest-temperature minerals form first, removing elements from the melt and shifting its composition so that different minerals become stable as cooling continues.

Olivine is stable at those highest temperatures and is therefore one of the first minerals to crystallize. Its early removal of magnesium and iron from the melt drives the remaining liquid toward the minerals that crystallize later at lower temperatures, such as pyroxene, amphibole, mica, and eventually feldspars and quartz. Quartz and most feldspars appear late, after the melt has become more silica-rich. Hence, olivine being among the first to crystallize best describes Bowen's Reaction Series.