A calc done by TataHakai here. Just putting it in blog format.
Altina used her left hand that should be wounded to grab a rock near her feet.
It was about the size of a human head.
Phew~, she regulated her breathing.
She seemed to be pumping herself up. The soldiers nearby gathered over to see what was the commotion about. Regis looked closely.
Altina yelled loudly. Some distance away, the cannons of the empire continued firing, emitting a earth shaking explosive sound.
At the same time-- The rock shattered. The rock in Altina's left hand disintegrated into pieces. This was no longer about injuries, but something shocking that seemed to be beyond the abilities of humans.
"To use as an amulet! For such a beautiful princess to crush iron ore with her bare hands is too amazing! It would definitely give blessings in shattering boulders!"
Average human head diameter = 17.5159235669 centimeters
Assuming the rock is a sphere since we have nothing else to go off
Volume = 2813.83 cc
Pulverisation of iron ore = 90 j/cc
2813.83 x 90 = 253244.7 joules (9-B, Wall level)
"About the size of a human head"
A human head has a height of 21.8 cm for 50th percentile.
Volume of the head = 4/3 * pi * (17.51592/2)^2 * (21.8/2) = 3502.041 cc
Energy of pulverisation of said rock = 315183.67 J (a higher Wall Level)