What is the world’s oldest musical instrument?  Scientists have found bone flutes that are thousands of years old.  Well what about stone instruments?  Hit two rocks together and you’ll certainly get some sort of sound.

I decided to make an instrument out of rock.  Here’s my “Stone Marimba” made using slate slabs.  Slate is a fine-grained metamorphic rock that can easily be split into smooth, flat pieces.  I saw one of these strange instruments and decided to make one.  Here it is, and here’s how I did it.

Here are three types of slate.  I found used slate roofing tiles.  Nice and thin, so that it would cut easier and sound good as a marimba bar.

I wore a full face mask, hearing protection and a respirator.

I found an old funky table saw and used a masonry blade (made to cut tile and stone).  Regular masonry saws usually have running water on the blade, but since I didn’t it threw up a lot of dust..and was very noisy.

I used this temporary bench to do the work.

I cut the bars to the same width (3.5 inches) and tuned them to length.  I checked the tuning with this small digital tuner.  If the bar is too low in pitch just cut the end of the bar or sand it.  If the pitch is too high you can glue small pieces at the end to lower the pitch.

Next I made two small block stands with fishing string.  I suspended the bar on the strings and poured salt on each end.  Tapping the bar with a mallet makes the salt move to the “node points”.  This is a point on the bar with the least vibration and a perfect place to suspend it for the best sound.  I marked the node points.

I used a masonry drill and drilled a whole at each end along the nodal points.  These holes are for the little pegs to hold the bar in place.

Next I attached weather stripping on each end along the axis of the node points.

The next step is to make the wood frame on which to mount the bars.  I made the frame so that it fit the node points from the longest to the shortest slate bar.

Here’s how the bars look mounted.  I put vinyl lettering to designate the pitches.

Here’s the finished Stone marimba.  It is one and a half octaves long.  I’m working on another octave lower and will also make higher pitches for a full range.

Here’s what it sounds like: