Drilling into fire place brick

[600rob]

Hi all. anyone able to identify the type of brick/material used in this fireplace recess?

I'm installing a wood burner and want to know if I can drill into this material and plug it ( with metal plugs) without splitting the brick in order to fit a frame to take a register plate

 

[foxhole]

Drill slowly and should be ok.Avoid hammer unless necessary .

 

[tomm12]

Stay away from the edge of the brick and start with small TC bit increasing bit size to plug size.