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Slate Stepping Stone (Tobi-Ishi) Large - Black
Slate Stepping Stone (Tobi-Ishi) Large - Black
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Specialist Aggregates Group
Specialist Aggregates Ltd Marine Arts
The most useful cleavage in the world
Monday 20 August, 2012
News Brief

Specialist Aggregates share the secrets of splitting slate rockery stone.

Full Story:

Cleavage, a word that has only relatively recently been associated with boobs and bums, has its origins in geological history, and a very useful attribute it is too.

Cleavage, or the ability of a rock to split cleanly in a given direction is shown to perfection with Welsh Slate. Our Black Welsh Slate Rockery is an excellent material for splitting into paving sized pieces suitable for edging ponds or walling, and we can now share some of the secrets of the slate producers.

Tools required: 100mm wide bolster chisel - preferably with a hand guard, lump hammer and thick working gloves.

A piece of slate is just like a book. The stone will probably have one or more flat sides or faces (Book covers), and possibly parallel stone ridges running along other sides (Pages). Just like opening a book the stone will split along these ridges and / or parallel to the flat face.

Place the stone upright but leaning slightly away from you on a firm surface. To use the analogy above, just like placing a book on a shelf, an additional piece of stone will probably be required as a “bookend”.

Place the cutting edge of the bolster chisel along the “pages” or parallel to a flat side – in the first instance just attempt to split the stone in half.

Strike the bolster chisel smartly with the lump hammer once or twice – force will not be needed if the correct splitting face (cleavage) has been chosen.

The stone should split (cleave) into two flat sided pieces, with new clean faces. It may help if the chisel is just twisted slightly as it enters the stone to bring the sides apart

Now you have the idea the fun is to see thin you can go. Whilst quality slate could potentially be split down to 1/32 of an inch (1mm), for practical garden applications splitting down to 1 inch ( 25mm ) will probably be sufficient!

Gardening Gloves: Freshly broken slate can be surprisingly sharp, and a miss with a lump hammer will smart!

Safety Specs: You shouldn’t be hitting the stones so hard as to produce rock splinters, but wearing safety specs is a sensible precaution.

Footwear: Wear stout footwear – you don’t want to be working any kind of stone in flip flops!, and with a bit of practice you can split the stone in a sitting position with boots acting as the “bookend”

The most useful cleavage in the world
The most useful cleavage in the world
The most useful cleavage in the world
The most useful cleavage in the world

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