pebble

As the last Ice Age came to an end, somebody picked a pebble out of a small river not far from Bethlehem..随着最后一个冰河时代宣告结束，有人从伯利恒附近流水淙淙的小溪边，捡起了一枚鹅卵石。

And what I do is, I select a hard stone hammer, in this case a quartzite pebble about the size of a cricket ball, and I elect to hit it in one place - and this is where I start to knap..“现在你瞧瞧，这儿呢，我挑了块燧石，比较细长的，要削薄下来工作量并不大。” “我要做的就是，选择一块够硬的石锤，这次我选这块是个头有板球大小的石英岩卵石。

pebble bed,卵石层，卵石床