Tuesday, October 23, 2012

A Malagassy Granite Quarry - by Gary

 Accounts of early pioneering life in Tasmania sometimes make reference to the high value placed on those convicts who possessed skills in quarrying and dressing stone, rendering it suitable for use in construction.  I reckon the present day granite quarry we saw in Nosy Komba must utilize very similar techniques to those employed by some of Australia’s earliest pioneers.

The Blacksmith Shop: the guy in the red shirt is turning up the heat in
this fire with a little hand driven air pump, getting blunt chisel tips red hot.

The Anvil:  when the chisels are hot enough they are worked
with a hammer and handy ‘anvil’ to reestablish a good point.

The Quarry Face:  This guy is using a chisel to make small holes in the rock
about 35mm in diameter and about 75mm deep and at about 250mm centres.

The Machine:  this guy is driving wedges down a line of holes (as created in the previous photo) to fracture this rock.


In the vertical rock face above you can see a line of wedge holes
 that have already been worked to fracture the rock.  A line of holes
in the horizontal face contain wedges that were being driven.

This is the guy working the line of wedges in the previous photo – in between sledge hammer blows he would carefully study the rock face and ‘sound’ it with light hammer taps.  He would also put a bit of water in each wedge hole (not sure why). You can see (in section) an older line of wedge holes at the top of the vertical face behind him.

This is the result they are looking for – a nice clean, even fracture .

Amazing work.

 Finished Product: roughly dressed building blocks 

Boys about Zeke’s age are hefting the finished blocks from the quarry down to the waterfront. 

Here blocks are being stockpiled on the beach for shipment across to Nosy Be (by sailboat of course).

Some of the work crew badly wanted me to take this group shot – as you can see, they are pretty fit and healthy specimens.

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