Very probable the hardness of protactinium was not measured up today because is very difficult to obtain a sufficient sample.
Extremely hard about 9.5 on Mohs' scale
Nickel has a hardness of 4 on the Mohs scale.
The Mohs hardness scale rating for brass is around 3 to 4.
Rutherfordium is a synthetic element and its hardness on the Mohs scale is unknown as it is difficult to measure. The Mohs scale is typically used to rank naturally occurring minerals based on their scratch resistance, so it may not be applicable to man-made elements like rutherfordium.
Sulfur is a relatively soft mineral, with a hardness of 2 on the Mohs scale. It can be scratched by minerals with a higher hardness, such as calcite (3 on the Mohs scale) and fluorite (4 on the Mohs scale).
Diatomite has a hardness of around 5.5 on the Mohs scale of hardness.
4
9 on the mohs scale
Quartz has a hardness of 7 on the Mohs scale, making it relatively hard and durable.
On the Mohs scale, 6.5 to 7.0.
3
The hardness of uranium is 6 on the Mohs scale; not so hard.
Iodine is not recognized as a mineral, and therefore is not assigned a number on the Mohs Scale of mineral hardness.
It is about 2.5 in the Mohs Hardness Scale.
look it up on the mohs scale
Glass is about 6-6.5
This scale is correctly called the Mohs scale. Scientists use this scale to measure a rock's hardness or softness. They can discover how hard a mineral or rocks is and drill in to it and find out more about it.