How hard is the human skull?

Human bones are very hard. If the hardness of steel is 7-8, the hardness of the hardest bone can reach 4-5, which is quite hard. Of course, the hardness of bones is different for different ages and people. The bones of teenagers and children are not hard, but soft, because there are organic and inorganic substances in them. Organic matter ensures the flexibility of bones, while inorganic matter is the hardness and strength of bones. When I was a child, there were many organic substances and few inorganic substances, so I was tough, but not hard enough. Adults, inorganic 2/3, organic 1/3, hard and strong bones. In the elderly, inorganic substances quickly decalcify and the quality of the whole bone decreases. Osteoporosis, the bones are not hard enough, and the old man fell and broke. Young people and adults generally have no problem wrestling. Even if the child falls, even if it breaks, it is also called a green branch fracture, such as a fracture, but the bone is tough and will not be completely broken. In addition, human bones, such as the femur, are strong enough, but the thinner finger bones are not strong enough, and some bones in the skull, such as the temple bones, are not strong enough, but the bones on the top of the head are hard. Therefore, the bone hardness of different parts is different, the bone hardness of different ages is also different, and the bone hardness of different nutritional States is also different, so in general, human bones are still quite hard.