scoria

plural scoriae · nonstandard plural rare scorias

1. countableuncountableengineeringThe slag or dross that remains after the smelting of metal from an ore.First known use 14th c.

   The like stuff is in Anacharsis: hot metal; full of scoriae, which should and could have been smelted out, but which will not.

   1837, Thomas Carlyle, The French Revolution: A History […], volume (please specify |volume=I to III), London: Chapman and Hall, →OCLC, (please specify the book or page number)

   Synonyms: cinder

2. countableuncountablegeographyRough masses of rock formed by solidified lava, and which can be found around a volcano's crater.First known use 18th c.

   To the south lay broken shapes of scoria in a lava bed as far as the eye could see.

   1985, Cormac McCarthy, chapter XVII, in Blood Meridian […] , →OCLC

   1 more example

   An excellent guidebook by Drs Kilburn and McGuire of University College London reveals that these unpromising pieces of debris are scoria and lithic fragments of the March 1944 eruption.

   2004, Richard Fortey, The Earth, Folio Society, published 2011, page 10

   Synonyms: cinders