How we turned 40 tons of igneous rock into a thing of beauty
On Mercer Island in 2007, Shepherd Stoneworks was hired to install this (among several other big-ticket items) at a waterfront property at the bottom of a very steep ravine.
I now call it The Basalt Forest.
The idea was to take columnar basalt spires of varying sizes, transport them down the long driveway and place them in a nice arrangement with some cement poured in and around the base for support. Soil was then later imported for this lovely planting.
Above is how the entire basalt column planter looked before being landscaped. This particular type of Columbia Basalt Column is referred to as "fluted" as it comes from part of the flow which has multiple narrow spires which often cling together into fatter fluted columns as opposed to the big and tall gray spires you often see. A few of these rocks weighed over two tons each.
Here is an example of basalt columns in the wild. This occurs over many millions of years as first basaltic stone is formed through minerals and exoskeletons falling to the bottom of the sea. Later through tectonic movement the sea floor becomes the mountain ridge. Then volcanic activity heats the stone in some places allowing for a certain crystallization of the rock.
Like all minerals, basalt has a given shape it takes on when crystallization occurs. In this case it forms vertical spires with a hexagonal or polygonal shape. This is shown in this shot from top of a range in Eastern Washington.
To quarry this, excavating machines carefully peel these apart while taking pains to avoid letting them topple and break.
Basalt is a very hard and dense type of stone comparatively, especially columnar basalt. Cutting through it with a diamond blade is almost as slow as cutting solid steel. Nevertheless, we also used the rubble from this quarrying process to make this dry-stone retaining wall. The polygonal profiles of the rocks were laid horizontally to interlock them as well as possible. As you see, columns were used to form the corners (planted deeply in the ground, of course) and to hold everything firmly in place.
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