## 1 Introduction  
Digital technologies that aim to transform the mining sector are attracting increasing attention from industry actors, policymakers, and investors. Amongst all these transformative technologies, blockchain is perceived as a means to render the raw material supply chain more transparent [1]. Supply chain transparency is often viewed as the essential element for solving many of the current trade and logistics challenges. Especially concerning the raw materials sector, greater transparency is often expected to solve key issues by ensuring product provenance and enabling traceability along supply chains. In particular, decentralized blockchain technology may guarantee greater data security and offer the opportunity to create digital assets and information with a high degree of immutability and transparency [2]. Yet, how can one ensure that the information entered into a blockchain is accurate, timely, and relevant? This paper explores different core features of blockchain and physical tracking technologies that address the following research questions:  
* How can blockchain technology, combined with physical tracking technologies, support supply chain transparency? * How can physical tracking technologies be categorized and structured in view of their applications and limitations, in order to create a simple taxonomy that can be relevant for tracking raw materials along supply chains? In order to illustrate the synergies between tracking technologies combined with the blockchain, we leverage our interpretation of the \"internet of things\" (IoT) and how this can support traceability. The concept of the IoT, has been defined as a \"network of interconnected electronic devices\" [3]. An additional definition has been \"a group of infrastructures interconnecting connected objects and allowing their management, data mining and access to the data they generate\" [4]. Whereas the connected objects have been defined as \"Sensor(s) and/or authenticator(s) carrying out a specific function and that are able to communicate with other equipment. It is part of an infrastructure allowing the transport, storage, processing and access to the generated data by users or other systems\" [4]. Due to its key features, which will be described briefly in Section 3, a blockchain can serve such an IoT infrastructure for interconnected physical trackers to allow their management, data mining, and access to the data they generate. In Section 4, a description of the Minespider blockchain shall illustrate its potential to track raw materials and provide transparency along complex supply chains, also by integrating physical trackers. Section 5 then outlines a simple taxonomy of key physical tracking technologies that, when linked to the blockchain, can further enable transparency within raw material supply chains. Ranging from barcodes to satellite communications, this research analyses the benefits, challenges, and use cases for these tracking tools when linked to the blockchain. These technologies are enablers of a broader trend, a global push for greater supply chain transparency and circularity by both practitioners and policymakers alike. For instance, the EU Commission is already pushing this agenda with the European Green Deal [5]. This is flanked by a Circular Economy Action Plan [6] and corresponding legislative procedures that are based on sustainability principles and mobilising the potential of digitalized product information. It shall include solutions such as digital passports, tagging and watermarks, as well as establishing a common European Dataspace for Smart Circular Applications with data on value chains and product information [6].