A frangible flapper valve that may be closed to hydraulically isolate a portion of a wellbore tubular. The flapper valve is made of a frangible material adapted to shatter upon impact from an impact sleeve. The sleeve may be used to initially hold open the flapper valve. A latching mechanism may be used to retain the sleeve above its initial position allowing the flapper to close isolating a portion of the tubular. The latching mechanism may engage a piston to retain the sleeve at the second position. A shearable device adapted to shear under a predetermined pressure selectively connects the piston to the tubular. When the pressure within the tubular increases above the predetermined amount the shearable device releases the piston and pushes the sleeve into the closed flapper valve causing the flapper valve to shatter. A second latching mechanism may prevent further movement of the sleeve.