Note, in versions predating v1.0.5, there is no difference between castle brick variants. Their respective hardness values, resistance etc. remain the same no matter the variant. In version v1.0.5+, Deepslate Castle Bricks along with End Stone have a slight edge in hardness and blast resistance.

In the latest version of CastleBlocks there are 13 different brick variants.

• Stone Castle Bricks
• Andesite Castle Bricks
• Granite Castle Bricks
• Diorite Castle Bricks
• Sandstone Castle Bricks
• Red Sandstone Castle Bricks
• Blackstone Castle Bricks
• Nether Castle Bricks
• Deepslate Castle Bricks
• End Stone Castle Bricks
• Purpur Castle Bricks
• Prismarine Castle Bricks
• Brick Castle Bricks

1.16 notably lacks Deepslate bricks.

• Stone Castle Bricks
• Andesite Castle Bricks
• Granite Castle Bricks
• Diorite Castle Bricks
• Sandstone Castle Bricks
• Red Sandstone Castle Bricks
• Blackstone Castle Bricks
• Nether Castle Bricks
• End Stone Castle Bricks
• Purpur Castle Bricks
• Prismarine Castle Bricks
• Brick Castle Bricks

In the backport to Forge 1.7.10 there are only two brick variants listed below:

• Stone Castle Bricks

• Sandstone Castle Bricks

Fun fact!, the stone brick textures for 1.7.10 retain the classic programmer art style!