Near-Infrared Absorption Characteristics and Quantification of Water Hosted in Internal Defects of Quartz

Quartz is an important industrial raw material, but water retained in internal inclusions and fractures can affect purification and melting quality. Rapid, nondestructive quantification of this water in granular samples remains challenging. This study investigated the relationship between near-infrared (NIR) absorption and releasable water in quartz from a banded iron formation (BIF)-related iron deposit. Ten particle-size fractions were prepared by stepwise mechanical crushing, and NIR reflectance spectra were measured over 760–2200 nm after standardized drying. As particle size decreased from 2–3 mm to <0.04 mm, absorption near 1400 and 1900 nm progressively weakened, while thermogravimetric analysis coupled with mass spectrometry (TGA-MS) showed that releasable water content decreased from 3.066% to 0.027%. Following multiplicative scatter correction (MSC), the spectra were normalized to a local reflectance continuum and converted to apparent absorbance. Integration of the band near 1900 nm yielded the water absorption area index (WAAI₁₉₀₀), which was used to calibrate an empirical square-root response model for releasable water content (R² = 0.991). This study provides a rapid, noncontact, and nondestructive laboratory spectroscopic approach for examining water-bearing defects and their variation among crushed size fractions. The approach also has potential for industrial batch screening and rapid identification of water-related absorption anomalies in quartz at mine sites. However, further experimental validation under industrial and field conditions is required before the approach can be applied in these settings.