Please post a picture with a short description of the characteristics. I found this rock on a hill in southern Iowa. There were none other like it. It is heavy for its size and magnetic. When I back light it, no light passes through it. The rock is soft and scratches easily. I can scratch it with my fingernail.
These short sentences let us know about the properties of a specimen. Lots of similar rocks tells us commonality, heavy and magnetic tells us, maybe metallic, it does not let light pass through it, so it is not translucent. It is soft, those short sentences each remove possible rocks from the possibilities and narrow the field in identifying it.