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LOOKING FOR A DIMENSIONAL STONE PROSPECT?
S.Narayana Moorthy

TIPS     Product Mix         Color     Hardness
 

All the igneous and metamorphic rock types are loosely termed under the term granite when applied to dimensional stone mining. Granite mining operations however differ significantly from conventional production mining especially with regard to blasting and excavation. It is very essential therefore that a mining engineer be involved from the exploration and evaluation stage itself. The list below helps greatly in evaluating a property for obtaining dimensional blocks:

• Regional setting and occurrence
• Grain size/texture/presence of moles (segregation, pyritisation etc)
• Joint patterns
• Contact zones/intensity of contact
• Shearing effects and spacing of shears
• Length and breadth of band (minimum and maximum width)
• Trenches to examine sheet rock
• Specific trend of dykes
• Good sheet rock free of defects at depth
• Area for present and future movement of machinery, explosive magazines, statutory safety zones and basic amenities
• Accessibility
• Area for spoil heap (far from deposit/near to workings)
• Influence of dwelling/ public roads/ power lines etc
• Availability of medical facilities, workshop and transport etc
• Availability of semi skilled and skilled personnel.

The evaluation of granite deposits is a very detailed and painstaking exercise, since the buyer largely determines the market. Considerations of color or variety often require working of very small deposits. It is also to be remembered that in most cases the demand for a particular color or variety fluctuates and the balance of infrastructure and establishment has to adapt to such fluctuations. A broad indication of product mix with classification, wear class, the end products as well as the mineral constituents that generally make up the color of the parent rock are tabulated below for use as a guideline. It is interesting to note that granite rocks are generally identified by the local name and variations of the color attached to it. Local peculiarities often radically determine the value of the block, given that the particular color/ variety is in demand at that point of time. 

1. Product mix

The joints and efficiency of recovery determine the product size and the product mix.

*Color represents local variety
**Percentage of production would determine the recovery of blocks

B. Color

The constituent minerals make up the color as it is applied to the parent rock (or granite). Please note that this is only a generalization and colors do vary from deposit to deposit.

C. Hardness

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