**2. Materials and Methods**

#### *2.1. Sampling*

The mixed Pb-Zn sulfide ore samples were collected from the Val Vedra mine in the Gorno Mining District, Lombardy, Bergamo, Italy. The Gorno mineralization is defined as MVT [17]; hosted mainly in Triassic shallow water carbonates [18]; and delimited in N-S, E-W, and NW-SE directions by 3 different tectonic faults [19].

About 30 kg of material was grab-sampled in the Pian Bracca extension area at level 1040 m a.s.l., currently under exploration for resource definition by Alta Zinc Ltd. [20]. In the Pian Bracca extension area, the mineralization is developed close to the low-angle Pian Bracca fault, hosted in a graphitic and carbonatic matrix and strongly tectonized, as described in detail by other authors [19].

#### *2.2. Characterization Methods for Samples and Products*

#### 2.2.1. Optical Microscopy

Optical microscopy (OM) was performed on uncovered polished 30-μm thin sections, realized from rock sample slices, using a Leica (Wetzlar, Germany) model Ortholux II POL-MK optical polarized-light microscope equipped with a DeltaPix camera and interfaced with DeltaPix software for image acquisition and processing. This was carried out using normal and polarized transmitted lights on polished thin sections for the determination of the main features of the mineralization and the average grain size of the target minerals.

#### 2.2.2. Scanning Electron Microscopy

Scanning electron microscopy (SEM) analyses were performed using a FEI (Hillsboro, OR, USA) model QUANTA INSPECT 200LV microscope equipped with an Energy Dispersive Analysis X-Ray (EDAX) detector and interfaced with xT Microscope Control and an Edax Inc. (Mahwah, NJ, USA) GENESIS Spectrum version 6.04 software. The measurement settings were high vacuum mode, 5.00 kV HV, and backscattered electron detector (BSED). Analyses were performed on uncovered 30-μm thin sections obtained from rock samples.

#### 2.2.3. X-Ray Powder Diffraction Analysis (XRPD)

X-ray powder diffraction (XRPD) analysis was performed using a Rigaku (Tokyo, Japan) model SmartLab SE diffractometer, with Copper K-alpha Radiation (CuKα) at 40 kV and 30 mA, 5–90◦ 2θ range, 0.01◦ step width, 1◦/min scan speed equipped with a D/teX Ultra 250 (H), and interfaced with the Rigaku (Tokyo, Japan) software SmartLab Studio II package. Quantitative phase analyses were performed by the whole-powder-pattern fitting (WPPF) Rietveld method [21–23], as implemented in the software. A pseudo-Voigt peak shape function was selected. The refined parameters were the phase scale factor, peak shape parameters, lattice parameters, preferred orientation, and structure coefficients. The ICDD PDF-4 2020 (International Center for Diffraction Data, Powder Diffraction File™) database [24] was used for phase recognition and refining. Powder samples were manually prepared using an agate mortar from oven-dried samples.
