  A mechanical diamond, a classical mechanics of a spring-mass model arrayed on
a diamond lattice, is discussed topologically. Its frequency dispersion
possesses an intrinsic nodal structure in the three-dimensional Brillouin zone
(BZ) protected by the chiral symmetry. Topological changes of the line nodes
are demonstrated associated with modification of the tension. The line nodes
projected into two-dimensional BZ form loops which are characterized by the
quantized Zak phases by 0 and $\pi$. With boundaries, edge states are discussed
in relation to the Zak phases and winding numbers. It establishes a bulk-edge
correspondence of the mechanical diamond.
