It is the opposite of "soft". It means that the material is very resistant to applied force.
When used as an adverb, it means with a great deal of effort.
It can also be slang for an erection.
Uranite is not correct, if you mean URANINITE, it is ranges 5-6 hardness.
It is about 2.5 in the Mohs Hardness Scale.
Kaolin has a hardness of about 2 on the Mohs scale. This means it is relatively soft and can be easily scratched with a fingernail.
Sodium has a Mohs hardness of around 0.5, which means it is very soft and easily scratched by harder materials.
Malachite has a hardness of around 3.5 to 4 on the Mohs hardness scale. This means it is relatively soft and can be easily scratched by harder materials.
Halite has a hardness of 2-2.5 on the Mohs scale of mineral hardness. This means it is relatively soft and can be easily scratched with a fingernail or a copper coin.
Galena has a hardness of about 2.5 on the Mohs scale of mineral hardness. This means that it is relatively soft and can be easily scratched with a fingernail or a metal object.
Feldspars generally have a hardness of 6 on Mohs' hardness scale.
They are almost as hard as rocks. The are considered a five hardness so that means about the same hardness as apatite. (a mineral)
Flint is a type of Quartz, and Quartz is a 7 on the Mohs Hardness Scale
Silver has a relatively low hardness compared to other metals, ranking around 2.5-3 on the Mohs hardness scale. This means it is malleable and can be easily scratched or dented.
An egg has a hardness of around 1-1.5 on the Mohs scale of mineral hardness, which means it is relatively soft and can be easily scratched by materials higher on the scale like fingernails or copper coins.