1
$\begingroup$
  • Scratches glass

  • Not affected by sandpaper on the bottom

  • Depending on lighting, intense light, triangles everywhere

  • Violet/light purple fluorescence

enter image description hereenter image description here enter image description hereenter image description hereenter image description hereenter image description here

$\endgroup$
  • $\begingroup$ What volcano (where)? What micro-geography (riverbed, road, ....)? Present in abundance or just a single object? Please edit your question. $\endgroup$ – Jan Doggen Oct 24 '17 at 12:18
3
$\begingroup$

It looks likes amethyst, which is a form of purple/violet quartz, often used in jewelry.

In the Brazilian state of Minas Gerais amethyst occurs with volcanic rocks.

$\endgroup$
  • $\begingroup$ That is an Amethyst, I've never seen anything else with quite the same colour and fracture combination. $\endgroup$ – Ash Oct 24 '17 at 11:46

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.