Quarrying is a specialist form of mining typically restricted to the extraction of building stone, e.g. granite, marble, limestone, sandstone. Most of this type of mining is surficial but some deposits are mined underground. Because each stone variety is individual and has been formed in different ways, and occurs in its own environment that has been subjected to a unique set of geological, geomorphological and climatic conditions, it follows that each quarry is different.
Environmental constraints, financial considerations, product quality and traditional (cultural) practices further dictate how each deposit of stone is worked. A wide range of methods is available for quarrying using very different machinery. The recognition of geological structures is fundamental to the choice of quarrying methods but there are many other factors that determine how each stone is quarried, by whom, to what size and in what quantity, for a set time. An intimate understanding of the make-up of the stone and its performance in use is also critical. As has been an often repeated situation there is no point in spending large amounts of money and quarrying stone that cannot be commercially quarried and sold. Only experience can deliver the best advice and results.
Hensel Geosciences has been quarrying stone commercially for 18 years utilizing a wide range of techniques in many different environments. Advice on best practice has been provided for many operators in Australia and overseas. Inspections of numerous local and overseas quarries to assess the resource, to determine commercial viability, and determine if the operators are capable of quarrying a certain amount of stone for a given project in the required time is an important but often neglected task.
Once quarried the stone needs to be processed for further use. Again, there are many techniques involved in stone processing and it is important to match the appropriate technique to the type of stone. Hensel Geosciences has been involved in the processing of many varieties of stone in many countries.
1. Project feasibility – an integrated assessment and evaluation of a dimension stone project incorporating many of the aspects below.
2. Quarry examination and evaluation through detailed geological investigation
- focussing on best siting
- variability throughout the deposit (inclusions, remnants, pegmatitic segregations, hydrothermal effect, metamorphism)
- structural controls (lineation, foliation, jointing, faulting, veining, dykeing)
- veining and sheeting with respect to potential wastage
- direction of quarrying in relation to the most desirable finished product
- reserve and yield calculations based on the geology and morphology of the deposit
- exploration and delineation of deposit; delineation of workable area; drill site selection; coring techniques
- drill cores assessment and description, sampling, cutting, and polishing
3. Quarrying methodology
- evaluation of the most appropriate quarrying techniques and equipment for a particular stone in relation to anticipated production and sales, climatic factors and environmental conditions
- assessment and recommendation of most appropriate quarrying machinery for the type of stone, again in relation to the anticipated production and sales
4. Training in the art of quarrying
- recognition of rock type and its intrinsic characteristics
- recognition of geological structures
- drilling techniques
- splitting techniques (wedges, expanding compounds, normal and specialized explosives, megajacks)
- maintenance of equipment
- block trimming
- block loading
- measurement and record-keeping
- ancillary products
- waste utilization
5. Block extraction
- short-term physical extraction of blocks for testing of stone (analysis of physical, mineralogical, chemical and geotechnical characteristics)
- testing of hardness (machinery selection)
- cuttability (machinery development)
- evaluation of processing and/or extraction costs, or for market assessment (local or global)