板岩 石板 蓝色 石片英释中释
There were several slates missing from the roof..房顶有几块石板瓦掉了。
clean slate,n. 清白历史
wipe the slate clean,勾销往事
on the slate,[英国口语]赊账，挂账
clean the slate,v. 了结往事；免除义务
