Minerals & Gemstone 480x104


Several detrimental habits are responsible for certain minerals to undergo chemical changes. Special conditions must be provided to preserve these minerals.

Efflorescence is the loss of water from the chemical structure of a mineral. A small number of hydrous minerals may partially lose the water in their structure if kept in dry or hot areas. This causes the mineral to form a white powder on its surface, and decreases its transparency. Some minerals eventually crumble from efflorescence.

Deliquesce is the opposite of efflorescence - it is the absorption of water into the chemical structure of a mineral. This property is only present in a few water-soluble minerals. Atmospheric water (humidity) gets absorbed into the structure of a mineral, thereby destroying its crystal lattice and causing it to dissolve. The most common delinquent minerals are Sylvite, Carnallite, and some specimens of Halite.

Some minerals transform into other minerals under stress, heat, and prolonged exposure to light. Some minerals, upon loss of water transform into other minerals. Three examples are:

  • Borax: Na2B4O7 · 10h1O
    transforms into Tincalconite - Na2B4O7 · 5H2O
  • Torbernite: Cu(UO2) 2 (PO4) 2 · 8-12H2O
    transforms into Meta-torbernite - Cu(UO2) 2 (PO4) 2
  • Autunite: Ca(UO2) 2 (PO4) 2 · 8-12H2O
    transforms into Meta-autunite Ca(UO2) 2 (PO4) 2

A well-known transformation is Realgar to Paraealgar. Bright red Realgar specimens transform into yellow Paraealgar when exposed to prolonged light.

A small number of minerals decompose in certain circumstances. Orpiment crumbles into a yellow powder when exposed to prolonged light. Marcasite occasionally develops a whitish encrustation on its surface that eventually causes it to disintegrate. This growth may spread to other sulfide minerals in a collection and cause them to disintegrate as well. This condition is not fully understood, and it only strikes certain Marcasite specimens at random. This condition, known as "Pyrite decay", is usually unpredictable.

Color Change
Some minerals undergo color changes in different lighting conditions or when exposed to radiation. For more information on this, see Color in mineral properties.

Advertising Information