grains of sand的用法和樣例：
例句
- A smooth, lustrous, variously colored deposit, chiefly calcium carbonate, formed around a grain of sand or other foreign matter in the shells of certain mollusks and valued as a gem.
珍珠在幾種軟體動物的貝殼中，圍繞著一粒沙子或其他外來物質形成的一種光滑、有色澤、具有不同顏色且主要是碳酸鈣的沉積物，被珍視為寶石 - We can see numberless grains of sand in a windy day.
在風天，我們能看到無數沙粒。
