靠窗外:我怀疑OP的石头是无聊的生物的结果。它相当是一个[白垩纪燧石][1]的白垩悬崖(如果存在)或在海滩上的海洋中被淘汰了。非常丰富的地区(和其他地方,如波罗的海)。这里包括@Orgong第二个例子,我认为这是一个燧石,太(也许不是cretacous),只是因为他们是如此的丰富。都可以检查是否打开。如果他们只显示一个白色的皮质内(外层)和非晶态和任何灰色到黑色的阴影,它显然是一个燧石。燧石是沉积岩的无定形氧化硅硅分泌生物。如果你打开一个大你甚至可以找到一个完整的(一个海胆化石骨架)[2]。它们形成结节的沉淀物,有时在分米的视野,结合邻居在这个过程中,形成板块,无论如何可以拥有任意形状包括凹或有破洞。流程详细描述例如[这][3]。 Sidenote: pretty good stuff for practicing stone knapping. Use a dense rounded sandstone as a pounder. And keep an easy wrist. It is all about the speed and angle, not the force. And do practice on a blanket to collect all the small flakes and chips or people will cut their feet when they wade through the remains of the workshop :-) [1]: https://en.wikipedia.org/wiki/Chert#/media/File:Flint_with_weathered_crust.JPG [2]: https://depositsmag.com/2017/11/02/humble-flint-sea-urchins-and-the-stories-they-tell/ [3]: https://ocw.mit.edu/courses/earth-atmospheric-and-planetary-sciences/12-110-sedimentary-geology-spring-2007/lecture-notes/ch6.pdf