— Palpation of tissue and organs during a surgical procedure provides clinicians with valuable information for diagnosis and surgical planning. In robot-assisted minimally invasive surgery (RMIS), lack of perceptible haptic feedback makes it challenging to detect a tumor in an organ or a calcified artery hidden in heart tissue. This study presents an automated tissue property estimation method and a realtime graphical overlay that allow an operator to discriminate hard and soft materials. We first analyze the properties of an artificial tissue and compare seven possible models. Selfvalidation as well as cross-validation confirm that the HuntCrossley model best describes the phantom tissue behavior and is suitable for our purpose. While the phantom tissue is palpated using a teleoperated surgical robot, the stiffness of the Hunt-Crossly model is estimated by recursive leastsquares. At the same time, a visual overlay is created using hue-saturation-luminance (HSL) on a semi-transpa...