## 1 Introduction  
The Permian stratigraphy of the Tuli Coalfield from the base to the top comprises the Tshidzi Formation, Madzaringwe Formation, Mikambeni Formation, and Fripp Formation [1]. The Madzaringwe Formation in the Limpopo Province of South Africa is a coal-bearing late Paleozoic units of the Karoo Supergroup [2]. Coal is an important organic sedimentary rock because it is used or serves as a source of electricity generation in most countries, especially South Africa. Coal is formed or usually reproduces over millions of years [2]. In general, coal is formed under different degrees of temperature and pressure over long periods. A progressive increase in pressure and temperature will, among others, form different types of coal. Coal type is related to the type of plant material in the peat and the extent of its biochemical and chemical alteration. Coal petrology deals with the microscopic identification of the different components of coal and measurement of vitrinite reflectance to determine the coal rank or quality. Hence, coal petrology is a very vital tool in the classification of coal deposits as well as coal products [3].  
The classification and characterization of coal for coke-making is significant because it allows for the selection of coals of a definite quality for specific coking operations and/or for estimating the quality of the coke that will be produced under certain conditions [3]. In the coke-making industry, \"the strength of metallurgical coke is one of its most essential properties, and possibly one of the most vital uses of applied coal petrography is the ability to predict coke strength (ASTM stability) from single coals and coal blends\" [4]. The coal rank and maceral constituent of coal affect the strength of the coke produced, and the ratio of reactive to inert macroals is of high importance when predicting the stability coke [5]. The reactive macroals are made up of vitrinite, liptinite, and semi-fusinite. The semi-fusinite is often used for South African coals to define a low-reflecting form of inertinite alleged to be reactive and which can increase or add to the reactivity of coal during carbonization [6]. The appraisal of South African coals for their coking characteristics entails a separate evaluation of the quantity of reactive semi-fusinite in the potential coal [7].  
The Madzaringwe Formation, which is the focus of this study, has about 120 m coal bearing unit and is the lowermost part of the Ecca Group in the Tuli Basin [5]. According to [8], the Madzaringwe Formation comprises three well-defined coal seams contained or hosted in a 150 m thick Main Coal Zone. These coal seams of the Madzaringwe Formation in the Vele Colliery are presently being mined. The Vele Colliery, which is the focus of this study, is geographically located between longitudes 29.56\({}^{\circ}\) E and 29.66\({}^{\circ}\) E and latitudes 22.15\({}^{\circ}\) S and 22.22\({}^{\circ}\) S (Figures 1 and 2). About 10% of the Vele Colliery core yard is underlain by coal-bearing strata, containing a valuable proportion of coking coal in South Africa [9]. However, up to date, the organic petrological aspects of these coal seams have not been taken into consideration. In this study, an effort has been made to carry out an organic petrological study on some selected coal samples from the exploitable coal seams phase (mature and economic) in the Vele Colliery to assess coal quality, thermal maturity/rank, and other intrinsic characteristics of the coal.  
Figure 1: Map showing the Limpopo Karoo basins and location of the study area within the Vele Colliery (after [10,11]).