What inspired me?
A stone pendulum.
 
I wasn't particularly looking for a pendulum, but found one while browsing in a local gift shop. Of the two basketsful, this was the one that spoke to me. It is Chevron Amethyst, also known as Dog Tooth Amethyst or Banded Amethyst.
 
A mix of Amethyst with White Quartz, this stone is found in many locations globally, including India, Russia, Madagascar and Brazil.
 
While there is a regular chevron pattern, the lines can be quite varied, in tone and width.
 
I made a painting in my sketchbook to capture the character of the stone, and was intrigued by the way the different lights and darks advanced and receded. 
 
While making a reference study in my sketchbook, I noticed that the different tones created a sense of depth. Enhancing this effect gave a 3D quality to the painting, so that the layers appear to hover above each other.
 
The pendulum was largely a uniform, rather dull, purple. Adjusting the colour gave more variety, from warm buff-pinks to cool blues.