板岩,其结构有变余结构、隐晶质结构，构造为板状构造。基本没有重结晶的岩石，是一种变质岩，原岩为页岩、泥质、粉砂岩或中性凝灰岩，沿板理方向可以剥成薄片。板岩的颜色随其所含有的杂质不同而变化，含铁的为红色或黄色；含碳质的为黑色或灰色；含钙的遇盐酸会起泡。一般以其颜色或成分命名分类，以颜色分类如绿色板岩、黑色板岩等，以成分分类如钙质板岩、炭质板岩、凝灰质板岩等。

在板岩地区，板岩可以用来作为屋顶的瓦使用，也可制成书写用的小黑板。

Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression.