This dataset comprises analytical, modeled, and imaging data of eclogitic clinopyroxene inclusions hosted in diamonds from the Cullinan Mine (South Africa) and the Rassolnaya Placer (Urals Mountains, Russia). Six inclusions containing varying proportions of spongy clinopyroxene (~10–100%) were selected to investigate the mechanisms of spongy clinopyroxene formation. In addition, we provide supplementary figures to Wang et al.(2025) to which these data are supplementary to.

Major element compositions of the primary cores and spongy rims of clinopyroxene were analyzed using electron probe microanalysis (EPMA). Pressure–temperature conditions were estimated using conventional thermobarometry and pMELTS modeling, which was also employed to simulate partial melting of primary clinopyroxene and the compositions of resulting melts and spongy clinopyroxene. Raman spectroscopy, FTIR, and photoluminescence data were used to assess volatile contents and structural features. Back-scattered electron (BSE) imaging and CT scans provide 2D and 3D textural constraints.

Data are organized into two main tables and ten supplementary tables (Tables S1–S10), which include sulfide inclusion compositions, Raman peak data, and modeling outputs. Fifteen supplementary figures (S1–S15) include BSE images, compositional variation plots, and CT scan visualizations. Two CT scan videos. All data are provided in open file formats (.xlsx, .docx, .avi), with accompanying metadata and documentation to ensure transparency and reproducibility.

Data collection took place between 2023.06 and 2025.01, and no physical sampling campaign was required, as the materials were sourced from curated diamond specimens. This dataset supports the manuscript “Formation of Spongy Clinopyroxene: Insights from Eclogitic Inclusions in Diamonds” and adheres to FAIR data principles.

(1) SEM-EDS, Mineral textures and compositions were analyzed using JEOL SEM instruments with EDS detectors at University College Cork (Ireland) and the Institute of Precambrian Geology and Geochronology, RAS (Russia). (2) EPMA, Major element compositions of inclusions were determined by EPMA at the Hebrew University of Jerusalem (Israel) and the University of British Columbia (Canada). (3) Raman Spectroscopy, Raman spectra of mineral inclusions were collected using a Renishaw InVia Qontor confocal Raman microscope at University College Cork, Ireland. (4) CT-scan, X-ray micro-tomography of inclusions was performed using a ZEISS Xradia 630 Versa μCT system at the American Museum of Natural History, USA. (5) pMELTS modelling, Geochemical modelling was performed using the pMELTS 5.6.1 Excel version to simulate partial melting of clinopyroxene inclusions over a range of pressure and temperature conditions. (6) Clinopyroxene-only thermobarometry, Crystallisation pressures and temperatures were estimated using the clinopyroxene-only thermobarometers of Putirka (2008) and Jorgenson et al. (2022), based on experimentally calibrated equations and machine learning models.