High Purity Calcium Sulfide (CaS) is a chemically refined form of calcium sulfide with impurity levels below 0.01 %, primarily used in optoelectronic phosphors, advanced ceramics, and specialty chemicals. Its high‑purity grade underpins performance‑critical applications such as blue‑green LEDs, laser host crystals, and high‑temperature refractory materials, making it a strategic raw material for next‑generation electronics and defense systems. The High Purity Calcium Sulfide market size is estimated at approximately USD 58 million in 2025, and the growth outlook projects a CAGR of 5.8 % through the market forecast period 2026‑2033, driven by rising demand for solid‑state lighting, expanding semiconductor manufacturing in Asia, and heightened defense spending on infrared and laser technologies. This industry expansion reflects broader macro‑economic trends such as the global push for energy‑efficient lighting, stricter emissions regulations that favor cleaner production processes, and increasing investment in advanced materials research.