Most distinguishing features:Resembles magnetite and ilmenite, but not very magnetic and has a more resinous lustre.
Industrial/economical uses:Only ore mineral for chromium.
Most distinguishing features:Hardness is best indicator, crystal habit is good too.
Industrial/economical uses:Used as a gemstone. High-quality ruby can be more valuable than diamond. Corundum is also used as an abrasive in sandpaper, polishing compounds, etc.
Most distinguishing features:Deep red streak and earthy lustre are indicative. SG may also be indicative.
Industrial/economical uses:Important ore or iron, sometimes used as a gemstone.
Most distinguishing features:Shining gray metallic lustre and deep-red streak are indicative.
Industrial/economical uses:Important ore of iron.
Most distinguishing features:Highly magnetic. Habit and colour are also indicators.
Industrial/economical uses:Mined for iron. Crushed magnetite also been used as aggregate to make high-density concrete for specialized applications, such as nuclear reactors.
Most distinguishing features:Will leave sooty marks if touched.
Industrial/economical uses:Manganese is used to colour bricks.