be of + 名词
语法:
“be of +抽象名词(词组)”
表示主语的某种形状或特征,相当于 "be+形容词"
例如: be of value=be valuable ; be of interest=be interesting; be of importance= be important
“be of+物质名词”
表示主语是“用某种材料构成或制作的”, 相当于be made of 或 be built of
如:Our building was of bricks.=Our building was built of bricks. 我们的楼房是砖建的
be of 表示"出生于"
例如:She was of good stock. 她出身很好.
CSDN , https://blog.csdn.net/fashion2014/article/details/66975954, 启明星的指引