Ok so in Grappler Baki chapter 291 is mentioned that Retsu’s strike stone was made of Obsidian instead of stone.
Then, in chapter 328, is explained that he broke it.
We don’t know how Retsu broke it anyways so I’ll use the thickness of the broke part itself.
Since Obsidian breaking thickness it’s irregular, I have 3 ideas of how to calc it.
One is use the lowest thickness part for a low end.
The second one is dividing it in three parts like if it was cut three times with sword of different thickness.
The third one is assuming the high part was fragmented since we can see some fragmented parts of obsidian in the floor.
Head: 72.9px (22.667cm) (Average human head)
Obsidian: 968px (300.1cm)
Obsidian Area: 7.073 (m)2
Obsidian tensile strength is 391.667MPa
Obsidian shear strength is 235MPa, or 235,000,000N/m2
End 1: Three cuts
Obsidian break A: 267px (83.018cm) thickness, 407px(126.548cm) diameter
Obsidian break B: 92px (28.605cm) thickness, 82px (25.497cm) diameter
Obsidian break C: 104px (33.336cm) thickness, 347px (107.892cm) diameter
End 2: Cut + fragmentation
Obsidian fragmentation: 267px (83.018cm) thickness, 157.572cm radius
Obsidian small break: 110px (34.202cm) thickness, 435px (135.254cm) diameter
End 3: Single cut
Obsidian Break: 65px (20.21cm) thickness, 849px (263.978cm) diameter
|Calculating Ends|
End 1: Three cuts
Obsidian break A: 7.073 (m)2 * 235,000,000n/m2 * 0.83018m * 1.26548m = 1,746,220,461.105692J
Obsidian break B: 7.073 (m)2 * 235,000,000n/m2 * 0.28605m * 0.25497m = 121,227,892.8431175J
Obsidian break C: 7.073 (m)2 * 235,000,000n/m2 * 0.33336m * 1.07892m = 597,825,246.3939366J
End 2: Cut + fragmentation
Obsidian fragmentation: (39,001.2cm2*83.018cm) * 391.667J/cc = 1,268,140,047.7272072J
Obsidian Small Break: 7.073 (m)2 * 235,000,000 * 0.34202 * 1.35254 = 768,905,806.927874J
End 3: Single cut
Obsidian break: 7.073 (m)2 * 235,000,000n/m2 * 0.2021 * 2.63978m = 886.758.924,58439J
Results:
End 1 (Three cuts): 2,465,273,600.3427455J, or ~589.214kg (Building level)
End 2 (Cut + fragmentation): 2,037,045,854.6550812J, or ~486.866kg (Building level)
End 3 (Single cut): 886.758.924,58439J or ~211.94kg (Small Building level+)
I calculated but didn't publicated it yet