This is a darkfield view of one of my beautiful "Herkimer Diamonds". They are spectacularly clear quartz crystals from New York State.
Note the small cavity within the crystal near the center. Its endpoints and adjacent planes parallel those of the crystal proper. Such cavities are pretty commom as are surface etch pits. Fortunately they do not diminish the beauty of these gems.
The crystal is a bit shorter than 1/2 inch.
Jim
Herkimer "Diamond"
Moderators: rjlittlefield, ChrisR, Chris S., Pau