Acoustic emission (AE) is an effective tool for revealing the rock failure mechanism. However, research has found that over 90 \(\%\) of test tensile failure sources cannot be captured. Furthermore, previous studies on thermal damage and AE characteristics have neglected the influence of mineral and grain boundary strength. Given this, this study establishes a Grain-Based Model that can accurately reflect the irregular shape of minerals. The model also considers the influence of minerals and intergranular strength. Firstly, an analysis is conducted to investigate thermal crack generation rules. Secondly, the quantitative investigation of temperature and grain size on AE properties is examined through moment tensor inversion. Finally, a comparative analysis explores the disparities in thermal crack generation and AE characteristics between different modelling methods. The results indicate that the phase transition of quartz causes significant structural damage, resulting in a sharp increase in microcracks. Additionally, the number of thermally induced cracks decreases as grain size increases. AE magnitudes exhibit a normal distribution with AE frequency and follow a power-law distribution with the cumulative number of AE events. The maximum magnitude gradually decreases with increasing temperature, while magnitude shows no significant correlation with grain size. The frequency of large-magnitude events decreases with rising temperature but increases with grain size. The formation pattern of thermally induced cracks and the distribution of AE failure sources strongly correlate with mineral and intergranular strength. Therefore, to accurately depict failure mechanisms in crystalline rocks, the models should consider the influence of mineral and intergranular strength.
