Smoky quartz's spiritual meaning is centered on grounding, protection, and the transmutation of negative energy into positive energy. It is associated with the root chakra and is believed to provide a sense of stability, strength, and security while helping to release fear, stress, and other unwanted vibrations. Historically, it has been used as a talisman for protection against negative forces. 
Spiritual properties and meanings
Grounding and stability: Smoky quartz is a powerful grounding stone that connects you to the Earth, providing a sense of stability and security.
Protection: It is considered a protective talisman, historically used to ward off negative energy, bad luck, and psychic attacks.
Transmutation of energy: This crystal is believed to absorb and transmute negative energy into positive ones, helping you to release negativity and move forward from difficult experiences.
Spiritual growth: It is seen as a guide for spiritual journeys, helping to focus the mind, overcome challenges, and achieve a higher state of being.
Emotional healing: The stone's supportive and stabilizing qualities can help release negative emotions like fear, anxiety, and sadness, promoting a sense of calm. 
Historical and cultural significance
Ancient use: Ancient civilizations, including the Celts and Druids, used smoky quartz for protection and believed it was a sacred stone connected to earth deities.
Alchemists: Alchemists used the stone in experiments, believing in its power to transmute negative energy.
National gem of Scotland: Smoky quartz is the national gem of Scotland, with the Cairngorm mountains historically being a source for it.