Soapstone is a metamorphic rock with which type of foliation?

• A. Schistose foliation
• B. No foliation
• C. Slaty cleavage
• D. Gneissic banding

Answer: (A)

Foliation forms when directed pressure causes minerals to align into planar layers. In rocks with abundant plate-like minerals such as talc, those minerals tend to line up into a schistose texture, giving a distinct, visible foliation. Soapstone is rich in talc and forms under low to moderate metamorphic conditions, so the talc crystals align parallel to the compression direction and produce schistose foliation. This is different from slaty cleavage, which is typical of very fine-grained slate with cleavage along tiny minerals, and from gneissic banding, which requires high-grade metamorphism that segregates minerals into light and dark bands. Since soapstone shows a pronounced, wavy sheeted alignment of talc, the foliation is schistose.