a dark-coloured rock containing a lot of small holes, formed by lava (= hot liquid rock) from a volcano

The sides of the hill were thickly covered with scoria. 山坡上覆盖着厚厚的火山渣。

The scoriae fragments are of all sizes from huge blocks down to minute granular dust. 火山残渣的碎片大小不一，从巨大的石块到细小的颗粒状灰尘都有。