  Currently, mass matrices are computed by means of sufficiently accurate
numerical integration schemes. Two-point and nine-point (Gauss) quadrature
remain frequently used. We derive an exact, easy to implement integration rule
for six-node wedge element mass matrices based on seven points only. Both
consistent and lumped mass matrices have been considered. New metric (jacobian
determinant) interpolation accompanied by analytical integration permits
computing effort reduction next to accuracy increase of integration rule. In
addition, one and four point mass matrices integration schemes have been
proposed. Accuracy superiority over equivalent schemes is established.
