a mineral can be scratched by a fingernail & if a mineral can be scratched by a fingernail then that mineral is soft ->  a mineral is soft  a mineral is soft & a mineral has a nonmetallic luster & if a mineral is black in color ->  that mineral is black, has a nonmetallic luster, and is soft  mica has a nonmetallic luster & mica is a kind of mineral & mica is black in color & mica is soft ->  mica is a mineral that is black, has a nonmetallic luster, and is soft  that mineral is black, has a nonmetallic luster, and is soft & mica is a mineral that is black, has a nonmetallic luster, and is soft -> that mineral is mica