The Steiner circle is the central circle with center at the nine-point center X_5 and radius R_S = 3/2 R, where R is the circumradius of the reference triangle. It is the circumcircle of the Steiner deltoid. It has circle function l = - (-a^6 + 3a^4 b^2 - 3a^2 b^4 + b^6 + 3a^4 c^2 + 6a^2 b^2 c^2 - b^4 c^2 - 3a^2 c^4 - b^2 c^4 + c^6)/(4b c(-a + b - c)(a + b - c)(-a + b + c)(a + b + c)), which is not a Kimberling center. The Steiner circle does not pass through any Kimberling centers.

central circle | second Steiner circle | Steiner deltoid