  This paper is concerned with the stress concentration phenomenon in elastic
composite materials when the inclusions are very closely spaced. We investigate
the gradient blow-up estimates for the Lam\'{e} system of linear elasticity
with partially infinite coefficients to show the dependence of the degree of
stress enhancement on the distance between inclusions in a composite containing
densely placed stiff inclusions. In this paper we assume that the inclusions to
be of $C^{1, \gamma}$, weaker than the previous $C^{2, \gamma}$ assumption. To
overcome this new difficulty, we make use of $W^{1, p}$ estimates for elliptic
system with right hand side in divergence form, instead of a direct $W^{2, p}$
argument for $C^{2, \gamma}$ inclusion case, and combine with the Campanato's
approach to establish the optimal gradient estimates, including upper and lower
bounds. Moreover, an asymptotic formula of the gradient near the blow-up point
is obtained for some symmetric $C^{1, \gamma}$ inclusions.
