The slabs for the polished variants of the stones and sandstone variants don't stack and don't show borders on the top/bottom variants. Please add a slab side texture for polished slabs and vertical slabs of these stones and change the models to make the slabs stack:

• Polished Granite
• Polished Diorite
• Polished Andesite
• Polished Blackstone
• Polished Marble
• Polished Jasper
• Polished Basalt/Voidstone
• Polished Limestone
• Polished Slate
• Quartz Block
• Biotite Block
• Sandstone
• Cut Sandstone
• Red Sandstone
• Cut Red Sandstone
• Soul Sandstone
• Cut Soul Sandstone
• Sandstone variants from compatibility mods like Atmospheric
• Cut Sandstone variants for the same sandstone mentioned above.

1. A lot of these slabs are not from Quark and
2. I'm pretty sure this is intentional. Smooth stone is the exception when it comes to stone variant slabs, not the norm.