Coal is considered to be a rock.
it is softer
Anthracite coal is harder than Lignite.
it is silver
The hardness of francium is not known.
Silver is softer than 18K gold.
Harder..One of the hardest things in the natural world.
Pedestal rocks are usually formed in desert, when wind erosion wears away softer rock under-laying a harder rock. The harder rock is eroded at a slower rate than the softer rock.
it is softer
Impossible to say, not knowing the definition of plain regular rock. There are some rocks harder than obsidian, while many are softer.
Limestone is softer than marble, but harder than chalk.
It's softer. #1 softest, #2 slightly harder, #3 harder than #2, etc.Softer.a #1 pencil is softer than a#2 pencil
Anthracite coal is harder than Lignite.
Depends on which one. Diamond is a metamorphosed coal/carbon that is the hardest natural substance known. Marble is metamorphosed limestone that is much softer. It's safe to say that all metamorphosed rocks are harder than they were in their pre-metamorphosed form.
Depends on which one. Diamond is a metamorphosed coal/carbon that is the hardest natural substance known. Marble is metamorphosed limestone that is much softer. It's safe to say that all metamorphosed rocks are harder than they were in their pre-metamorphosed form.
Weathering and erosion.
DENTIN
calcite