Abstract: Micaceous-cordierite-glass ceramic particularly suitable for stomatological, head surgery and neck surgery applicatiosn has a fracture toughness K.sub.IC of up to 2.0 MPa m.sup.1/2, a hardness HV.sub.0.07 of 300-1000, a compressive strength of up to 450 N/mm.sup.2, a linear thermal expansion coefficient of 75-125.times.10.sup.-7 K.sup.-1, good chemical stability and excellent machinability as well as a high resistance to wear and comprises a composition in weight percentages of______________________________________ SiO.sub.2 43-50 Al.sub.2 O.sub.3 26-30 MgO 11-15 R.sub.2 O 7-10.5 F.sup.- 3.3-4.8 Cl.sup.- 0.01-0.6 CaO 0.1-3 P.sub.2 O.sub.5 0.1-5 ______________________________________wherein R.sub.2 O is the sum of 3 to 5.5 wt. % Na.sub.2 O and 4 to 6 wt. % K.sub.2 O, a first crystal phase of mica, and a second crystal phase of 5 to 30 volume % cordierite, wherein relatively large mica crystals of 10 to 200 .mu.m are embedded in the glass and cordierite crystals of 0.5 to 5 .mu.m are arranged in the glass.