Muscle Relieving Massage Stone Alder New York's Gua Sha Tool is made from black obsidian, a natural crystal formed from rapidly cooling lava. Gua sha is a traditional Chinese medicine practice designed to help improve overall health by massaging the skin with the aid of gua sha tools. This smooth heart shape stone helps relieve tension, reduce puffiness, and promote circulation. Use morning and/ or night to improve overall skin health and appearance by stimulating collagen, massaging tense muscles, and promoting lymphatic drainage. Each tool is unique and may have slight variations due to the organic nature of the stone. Handle with care. Clean gua sha tool with a damp cloth and/ or rubbing alcohol.