MixMaterial Data
You might be wondering what mixmaterial names are?
well basically its a collection of materials that bind to a certain name so that more customizations are possible:

ok? well how do i create one?

Open up the themes.yml in the BiomeData folder. Simply add a line like so :
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stonemix: "DIORITE,ANDESITE,STONE,GRANITE"
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# materialmixname: "Materials seperated by ,"
Copied!
as soon as the server restarts the data is loaded to worlds using it.