Well, I think a mineral that is crystalline reflects the light only by total internal reflection in air medium. Hence, even if it is a black mineral, it can still appear shiny. So, the mineral should still appear lustrous but may appear that it is being seen in a low light..
Luster
luster
Luster
When a mineral reflects light it can have a metallic a nonmetallic or a brilliant luster
Luster
Luster is the way a mineral reflects light.
Luster
luster
luster
Luster
Luster
Luster - The way in which a mineral reflects light.
When a mineral reflects light it can have a metallic a nonmetallic or a brilliant luster
luster
luster
Luster describes how a mineral reflects light
Luster