Chalcopyrite (Portugal 1971)

Stamp Chalcopyrite it reflects the thematic directions:

A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewelry or other adornments. Certain rocks (such as lapis lazuli, opal, and obsidian) and occasionally organic materials that are not minerals (such as amber, jet, and pearl) may also be used for jewelry and are therefore often considered to be gemstones as well.Most gemstones are hard, but some softer minerals such as brazilianite may be used in jewelry because of their color or luster or other physical properties that have aesthetic value. However, generally speaking, soft minerals are not typically used as gemstones by virtue of their brittleness and lack of durability

Geology (from Ancient Greek γῆ (gê) 'earth', and λoγία (-logía) 'study of, discourse') is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth sciences, including hydrology. It is integrated with Earth system science and planetary science.

In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form

A conference is a meeting, often lasting a few days, which is organized on a particular subject, or to bring together people who have a common interest. Conferences can be used as a form of group decision-making, although discussion, not always decisions, is the primary purpose of conferences. The term derives from the word confer.