The coolest thing about this metal is how you can color it without use of any paints or dyes simply by oxidizing a microscopically thin layer. This is done by immersing a piece of niobium in an electrolytic bath and passing a current between it and a sacrificial anode. Niobium at the cathode end rapidly oxidizes with the voltage determining how deep the oxidation layer goes. At around 12 volts you get brown and then all the colors of the rainbow as you turn up the juice.

Except red. Nature has let Niobium dress in any color except fire hydrant red. We can perhaps look to Greek mythology for a reason. Niobe was the daughter of Tantalus (see a connection here?) and, due to a careless comment, had all 14 of her kids immediately executed. Zeus took pity and turned her into a rock whose eyes continue to cry to this day in the form of a hilltop stream known as "the Weeping Rock" in Turkey. Maybe in the ineffable language of the gods red is a reminder to watch your mouth?

10mm cube weight is 8.6±0.1g.

25.4mm cube weight is 141±0.5g.

50mm cube weight is 1,075±2g.