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

其中一段灰色的德里石英岩墙已经倒塌。

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

哥伦比亚大学的地球化学家在印度洋昂儒昂岛上发现了一个石英岩矿脉，石英岩是由砂岩形成的变质岩。

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， 包括砂岩、绿石和石英岩。