Can you find opals in stagties caves where water been flowing for thousands of years

Which is not true about oxygen-17 and oxygen-18?

What are similarities and differences between refraction, reflection, diffraction and absorption?

Two rigid transformations are used to map δhjk to δlmn. the first is a translation of vertex h to vertex l. what is the second transformation? a reflection across the line containing hk a rotation about point h a reflection across the line containing hj a rotation about point k