One section of its walls of grey Delhi quartzite had collapsed.

其中一段灰色的德里石英墙已经倒塌。

Geochemists at Columbia University found a lode of quartzite, a metamorphic rock formed from sandstone, on the Indian Ocean island of Anjouan.

哥伦比亚的地球化家在印度洋昂儒昂岛上发现了一个石英矿脉，石英是由砂形成的。

This is because the stone balls were made of different types of stone including sandstone, green stone and quartzite.

这是因为石球是由不同类型的石头制成的， 包括砂、绿石和石英。