As4S4, also known as arsenic sulfide, is a chemical compound composed of four arsenic (As) atoms and four sulfur (S) atoms. It typically appears as a yellow or orange solid and is known for its use in various applications, including the production of pigments and in the glass industry. This compound can exist in different forms, with the most common being the stable form called orpiment. Arsenic sulfide is also of interest in mineralogy and can be found in nature as a mineral. However, it is important to handle it with care due to the toxic properties of arsenic.