unknown sedimentary rock

Description

This rock is made of a dense colletcion of fine material that is not visible with the naked eye or hand lens. The rock is a deep black color all over but upon close inspection it demonstrates shiny sections and layers amidst the blackness. The rock is relatively hard but doesn't scratch a glass scratch plate at all. The rock is void of fossils. The rock doesn't taste salty. If exposed to a flame this rock ignites and produces flame for a fair amount of time. rocksandminerals CC BY(4.0) via sketchfab [https://creativecommons.org/licenses/by/4.0/legalcode]