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magnetite
Well you see, it's pretty simple. If a fingernail has a hardness of 2.5, and the question is asking what mineral can easily be scratched by a fingernail. Well then it is Graphite. It has a less hardness than your fingernails.
Depending on the variety, feldspars can range from adamantine to glassy in luster.
Mica has a non-metallic luster, one called vitreous or glass-like.
These words indicate the luster of a mineral.
Magnatite is the mineral that has a nonmatallic luster, is black, and can be scratched by a fingernail.
That could be graphite, which is a natural allotrope of the element carbon.
Well you see, it's pretty simple. If a fingernail has a hardness of 2.5, and the question is asking what mineral can easily be scratched by a fingernail. Well then it is Graphite. It has a less hardness than your fingernails.
If a mineral has a shiny luster, is it matallicIf a mineral has no shiny luster, is it nonmetallic?
Gypsum
magnetite
Well you see, it's pretty simple. If a fingernail has a hardness of 2.5, and the question is asking what mineral can easily be scratched by a fingernail. Well then it is Graphite. It has a less hardness than your fingernails.
azurite is one of the minerals that has a light blue streak.
luster
hematite can have both metallic and nonmetallic luster.
The Luster of a mineral is it's appearance in the light. Also there are two types of Luster, metallic and nonmetallic.
There is not enough information to go on. Many minerals fit this description, especially since there are several types of nonmetallic luster.