Fig. 7: Macroscopic and microscopic characteristics of the samples.

a, b Sample SXD-20. c Sample SXD-72. d Sample SXD-79. a Under plane-polarized light. b–d Under cross-polarized light.

a, b Sample SXD-20. c Sample SXD-72. d Sample SXD-79. a Under plane-polarized light. b–d Under cross-polarized light.