The word periclase 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: 16
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (37 words)
caliper, carpels, cereals, clasper, eclairs, eclipse, escaper, icespar, leapers, parcels, pierces, placers, pleaser, precise, presale, realise, recipes, reclasp, reclips, relaces, relapse, repaces, repeals, repiles, replace, replica, replies, rescale, reslice, respace, respice, scalier, scalper, sclerae, spacier, special, splicer