Definition of "marlstone" [marl•stone]

• A rock containing clay materials and calcium and magnesium carbonates, with approximately the same composition as marl. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Yes, it's local stone, called marlstone – basically a limestone that has iron in it, I think, hence the lovely rusty colour."
• "On the left is a ruined castle, built of shelly marlstone, which, according to Arabian tradition, once belonged to the Berdovil in question."
• "When there is an upper story, which is rarely the case, it is approached from the courtyard by a staircase, usually dilapidated, with stairs of shelly marlstone."