tectonic grain

例句：

1. 1.The tectonic grains of the rock are visible through a microscope.
   通过显微镜可以看到岩石的构造颗粒。
2. 2.The study of tectonic grains is crucial for understanding earthquakes.
   研究构造颗粒对于理解地震至关重要。
3. 3. The grains of sand were so fine that they could be seen through the eyepiece.
   沙子的颗粒非常细，可以通过目镜看到。