granite is grey in color and has crystals of mica, quartz all embedded in it, giving it a shiny and silver appearance
It's called the minerals streak
gray and orange will make an ugly muddy color
Brown
gray
You don't really measure luster, rather it is a yes or no answer. And in this case Aluminum does have luster.
The color of a metallic streak is typically a dark gray or black color. This is because the streak left behind by a metallic mineral is the color of the powdered form of the mineral, which is often dark due to the presence of metal atoms.
The mineral that leaves a grey streak and is metallic is likely hematite. Hematite is a common iron oxide mineral that has a metallic luster and leaves a grey streak when scratched against a rough surface like unglazed porcelain.
A streak of graphite is the mark left on a surface when graphite is rubbed across it. It is typically a shiny, metallic gray color. Graphite's streak is often used as a diagnostic property to help identify minerals.
Nickel leaves a silver-gray streak. Note that nickel is an element.
The same color as the writing from a pencil, very dark grey or black. Pencils used to be made of graphite
Could be: Chalcocite, Galena, Molybdenite, Stibnite, or Jamesonite.
dark gray, brown, greenish
Galena mineral typically appears with a streak color that is gray to black.
The streak color of bauxite is usually white to gray.
Hornblende's streak color is typically white to gray.
The streak color of gabbro is white to gray.
Promethium is so rare and so radioactive I don't thing anyone's ever collected enough of it to tell. It would, however, presumably be a silvery-gray color like nearly all other metals.