21. The pyrite concretions typically are about 30 cm ( 1 foot ) in diameter. 22. The structure is very futuristic, and it is similar to a coralline concretion . 23. It contains large ( up to 15 feet in diameter ) sandy calcareous concretions . 24. Do similar indented concretions exist in other areas? 25. The arthropods in the upper member of the Barstow Formation are preserved in concretions . 26. It is the most common beetle found in the concretions from the Barstow Formation. 27. Large calcareous concretions commonly occur within this formation. 28. In the second room, there are also quirky and stalactites concretions like swords. 29. The process that created the septaria, which characterize septarian concretions , remains a mystery. 30. The surface of these spherical concretions can range from being very rough to quite smooth.
