A type of rock composed of minute crystals that are not visible to the naked eye.

सूक्ष्म-क्रिस्टलीय चट्टान

English Usage: The geologist studied the micro-crystalline rock to understand its formation.

Hindi Usage: भूविज्ञानी ने सूक्ष्म-क्रिस्टलीय चट्टान का अध्ययन किया ताकि इसके निर्माण को समझा जा सके।