premise: mica has a nonmetallic luster sent2: a mineral can be scratched by a fingernail sent3: mica is a kind of mineral sent4: if a mineral can be scratched by a fingernail then that mineral is soft sent5: mica is black in color sent6: a mineral has a nonmetallic luster sent7: if a mineral is black in color sent8: mica is soft.
hypothesis: that mineral is mica