This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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adj. Readily crumbled; brittle: friable asbestos insulation.

adj. Easily broken into small fragments, crumbled, or reduced to powder.

adj. Loose and large-grained in consistency.

adj. Likely to crumble and become airborne, thus becoming a health risk

adj. Easily crumbled, pulverized, or reduced to powder.

Easily crumbled or pulverized; easily reduced to powder, as pumice.

adj. easily broken into small fragments or reduced to powder

"And then there's non-friable, which is generally found on the inside and does become easily airborne."

breakable   

crumble    crumbly   

marly    ferruginous    calcareous    siliceous    argillaceous    porous    crumbly    spongy    well-drained    flaky