There are a few things to consider when thinking about the answer to this question. The first is the hardness of each material. Diamonds are the hardest known natural material, while obsidian rates at about 5-6 on the Mohs scale of hardness. This means that diamond will scratch anything below it on the Mohs scale, including obsidian. So in terms of hardness, diamond is stronger than obsidian.
The next thing to consider is their density. Density is how much mass an object has for a given volume. Diamonds have a very high density, meaning they are very heavy for their size. Obsidian is less dense than water, so it’s actually lighter than diamonds! But because diamonds are so hard, they can withstand more pressure than obsidian can. So in terms of density, diamonds are stronger than obsidian as well.
The last thing to consider is their heat resistance. Both materials can withstand high temperatures, but diamonds have a higher melting point than obsidian does. This means that diamonds can take more heat before they start to break down and change shape. So in terms of heat resistance, diamond is stronger than obsidian once again!
When you put all of these factors together, it’s clear that diamond is stronger than obsidian overall. But both materials have unique properties that make them useful in different ways!