Collectible specimen

Mineral specimens are collected for crystal form, colour, rarity and locality, and the criteria are closer to those of art than of science — a well-formed crystal from a famous and exhausted locality is worth many times an identical one from an operating mine.

Locality is the part outsiders underestimate. A specimen's value depends heavily on where it came from and on that provenance being documented, which is the same argument this site makes about evidence, arrived at independently by the people who collect them.

• Material

  Amber

  for the inclusions rather than the amber — an insect in Burmese amber is a Cretaceous fossil that a mineral specimen cannot compete with

• Mineral variety

  Amethyst

  The purple variety of quartz, coloured by iron impurities and natural irradiation.

• Mineral

  Fluorite

  for its colour range and its fluorescence

• Mineral

  Galena

  for the cubic cleavage, which is unusually perfect

• Alloy

  Neodymium magnet

  sold as toys and desk objects, and the subject of repeated safety recalls after children swallowed more than one

• Rock

  Pegmatite

  the source of most large, well-formed crystals in museum collections

• Mineral

  Quartz

  The second most abundant mineral in the Earth's continental crust, and the reference point for hardness 7 on the Mohs scale.

• Mineral

  Vanadinite

  for the colour and the sharp hexagonal habit

• Mineral

  Wulfenite

  the square orange tablets are among the most recognisable in mineralogy

Each of these uses is established and cited on its own. Whether something counts as an ore, for instance, depends on grade, price and era — and those qualifications are shown alongside it.