(铅笔芯)硬黑用英语怎么说

铅笔芯 (pencil lead) 硬黑 (hard black) 用英语可以说作 "graphite". 来源是铅笔由于使用了石墨 (graphite) 而得名。

"The pencil lead is made of graphite." (铅笔芯由石墨制成。)
"I prefer to write with a pencil because the graphite is darker and harder than a pen." (我喜欢用铅笔写字，因为石墨比笔黑而且更硬。)
"The graphite in a pencil is a form of carbon." (铅笔中的石墨是碳的一种形式。)