The dataset comprises 3D micro XCT scans collected with a ZEISS Xradia Versa 410 at the Istituto Nazionale di Geofisica e Vulcanologia-Osservatorio Vesuviano (Italy). Samples are ash particles within the 0/-0.5 φ (1-1.4 mm) grain size range collected from different stratigraphic horizons (C, F, I, L, O) of the type section (KF176) of the 4ka Rungwe Pumice Plinian eruption (Tanzania). A total of 4001 bidimensional X-ray absorption projections were collected during a 360° rotation of the sample at 80 kV and 7 W. For each sample a scan was collected using a 10x magnification lens, additionally, for specific samples, a further scan with a 20x lens was also collected at 150 kV and 10 W. The pixel size results in 2 µm/px (8 µm^3/voxel) for samples scanned with 10x lens and 1.1 µm/px (1.3 µm^3/voxel ) for samples scanned with 20x lens. When necessary, a low-energy (LE1) filter was used to minimise beam hardening. The scans were then reconstructed into tomographic volumes using the integrated XRM Reconstructor software.