#2. Minerals, Rocks and Gemstones.

Basic definition of a mineral:

The general definition of a mineral encompasses the following criteria

1. Naturally occurring
2. Stable at room temperature
3. Represented by a chemical formula
4. Usually abiogenic
5. Ordered atomic arrangement

The first three general characteristics are less debated than the last two.

The first criterion means that a mineral has to form by a natural process, which excludes anthropogenic compounds.

Stability at room temperature, in the simplest sense, is synonymous to the mineral being solid at 25°C. Classical examples of exceptions to this rule include native mercury which crystallizes at -39°C, and water ice, which is solid only below 0°C.

Modern advances have included extensive study of liquid crystals, which also extensively involve mineralogy. Minerals are chemical compounds, and as such they can be described by fixed or a variable formula. Many mineral groups and species are composed of a solid solution; pure substances are not usually found because of contamination or chemical substitution.

The formal definition of a mineral approved by the IMA in 1995:
A mineral is an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes.

In addition, biogenic substances were explicitly excluded. “Biogenic substances are chemical compounds produced entirely by biological processes without a geological component (e.g., urinary calculi, oxalate crystals in plant tissues, shells of marine mollusks, etc.) and are not regarded as minerals. However, if geological processes were involved in the genesis of the compound, then the product can be accepted as a mineral.

To put it in a nutshell…
All gemstones are minerals but all minerals are not gemstones.
All minerals are rocks but all rocks are not minerals!