Abstract: Xiangshan volcanic rock had been named "Lava with cracked phenocrysts" by many authors in recent years. Using the method for analysis of grain-to-grain stress effect we had found evidence on rock compaction. The so-called cracked phenocrysts may be the result of converged grain-to-grain stress effect. For this reason, the petrogensis of these rocks took place under the action of compressive stress, and the rocks were formed by the accumulation of pyroclastic debris. They can be classified to volcanic tuff. After the tuff diagenesis, they once again were subjected to thermal metamorphism and then recrystallization. Thus the rocks exhibit some untypical properties.