(In Minecraft BE)Inside the Basalt Delta (below the surface or above the ceiling),all are netherrocks. Only on the surface and ceiling can generate the basalt or blackstone. (In Minecraft JE)But in Minecraft JAVA Edition,the rocks in Basalt Delta are dominated by basalt. And the netherrocks,blackstones will be generated as veins.I hope the offical will optimize Basalt Delta in Bedrock Edition.