[求助]04.10.37语法请教，谢谢：）

37. Among the most complex crystals are that of silicon dioxide, which has seven different structures at various temperatures and pressures, the most common being quartz.

请问一下，the most common being quartz.在句子中是什么成份阿？为什么要用being？

很像是独立主格结构

the most common是逻辑主语  用分词做逻辑谓语