The fresh surface of neptunium is silvery.
Neptunium has a metallic appearance.
dull
dull luster looks somewhat metallic, but it isn't quite as reflective.
the luster is dull or some metallic.
it is dull
it is dull
Granite has a very dull luster when unpolished.
dull to pearly to subvitreous
Xenon is a colorless, odorless, and tasteless gas at room temperature, so it does not exhibit any luster.
In geology, dull luster means little to no luster is exhibited by a mineral. This is due to coarse granulations which scatter the light in all directions.
The words waxy, pearly, and dull describe a mineral's luster.
the type of luster which is dull