Deepslate ores can only be smelted in a blast furnace.

To continue on the idea that deepslate is tougher or stronger than stone some people said you have to use a higher tier pickaxe to mine the ores. https://feedback.minecraft.net/hc/en-us/community/posts/360077240411-Deepslate-ores-should-require-higher-tiers-of-pickaxes-to-break 

It already takes twice as long to mine the ores so I don't think this is necessary. Someone said all deepslate ores should have to be smelted this is also a good idea. https://feedback.minecraft.net/hc/en-us/community/posts/360077298172-All-Deepslate-Ores-need-to-smelt 

I was thinking because deepslate is so strong you can only smelt the ores into ingots and the cobbled version into normal deepslate inside the blast furnace. 
Thank you, Mojang for such an amazing game!!!