The word marlstone is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 14
Highest Scoring Words With Friends™ Play In The Letters marlstone
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Seven Letter Word Alert: (36 words)
almoner, anomers, antlers, armlets, artsmen, atoners, enamors, laments, leantos, loaners, maestro, maltose, mantels, mantles, martens, matrons, mentors, meronts, moaners, monster, morales, mortals, normals, oarsmen, orleans, reloans, rentals, reslant, saltern, senator, smarten, sternal, stromal, tonearm, tramels, treason