This bug has existed for a while but has yet to be fixed. Affected blocks:
Block of Quartz
Bottom of the block has Smooth Quartz Texture (seamless)
Quartz Stairs
Bottom of the block has Smooth Quartz Texture (seamless)
Glitching issue on corner blocks
Quartz Slab
Bottom of the block has Smooth Quartz Texture (seamless)
Appears darker than blocks under the same light level condition (not always)
Smooth Quartz Block
Same texture as regular (not seamless except for the bottom)
Smooth Quartz Stairs
Same texture as regular (not seamless except for the bottom)
Glitching issue on corner blocks
Smooth Quartz Slab
Same texture as regular (not seamless except for the bottom)
Appears darker than blocks under the same light level condition (not always)
Related bug: Block of Quartz in the Grindstone makes Smooth Quartz Slabs instead of regular
Hopefully we can finally get these sorted out.
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TheΒ
Linked issues
Comments 1

Thank you for your report!
We're already tracking this issue at MCPE-42276, so I will resolve and link this ticket as a duplicate. If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
You mentioned two things that aren't covered in the main ticket: Glitching on the corners of stairs, and darkening of slabs. The darkening is a previously reported lighting bug (that also applies to the full block and, I assume, stairs). I'm not sure what you're calling "glitching"; perhaps it's something like Z-fighting, which might well be part of the same problem. If you feel it needs to be addressed separately, please create a new ticket and attach a video showing the effect you're talking about.
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