The Nickel-Strunz Mineral Classification: Native Elements Explained

The Nickel-Strunz Mineral Classification: Native Elements Explained

Introduction to Native Elements

Native elements or minerals include well-known materials like gold, silver, and diamonds. These naturally occurring elements have unique properties that set them apart from other mineral classes. Understanding the Nickel-Strunz classification of native elements can provide valuable insights into the formation and characteristics of these fascinating geological wonders.

What are Native Elements?

Native element minerals are defined as single-element minerals or naturally occurring metallic alloys. Of the 118 known elements featured on the periodic table, only 19 can occur naturally in a native form. This means they can create a crystal structure without combining with other elements. Native elements share some characteristics (with exceptions, of course). All native elements are chemically inert or non-reactive. This allows them to create minerals with only one type of atom. The most well-known native elements are gold (Au), silver (Ag), diamond (C), and sulfur (S).

The Native Elements Mineral Class

The native elements mineral class can be divided into three groups: metals, semimetals, and nonmetals. Each group exhibits unique properties and characteristics.

Metals

The metal group of native elements can be further divided into three sub-groups: the gold sub-group, the platinum sub-group, and the iron sub-group.

Gold Sub-Group

The gold sub-group includes not only gold but also silver, copper (Cu), and lead (Pb). These metals are relatively soft, malleable, and ductile, with low melting points. They are also good conductors of electricity and heat.

Platinum Sub-Group

The platinum sub-group of native elements — also known as platinoids or platinum-group elements (PGEs) — consists of six elements with similar properties. They are ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt).

Minerals of the platinum sub-group are harder and have higher melting points than those of the gold sub-group. For example, osmium has a melting point of 3,033° C, while gold has a melting point of 1,064° C. Platinum native elements also have high densities. For example, platinum has a density of 22 g/cm3, while gold has a density of 19.3 g/cm3.

All platinum sub-group members have very similar atomic radii, which makes substitutions for alloy formation relatively easy. As a result, these native elements never occur in pure form.

Iron Sub-Group

The iron sub-group of native elements consists of iron (Fe), nickel (Ni), and their alloys.

You will rarely find iron in its native form on the Earth's surface. Iron is more chemically reactive than any of the metals covered so far. Iron tends to combine with oxygen or sulfur. Iron-nickel alloys are found primarily in meteorites because forming native iron and nickel requires an exceptionally oxygen-starved environment, such as outer space. According to one theory, the Earth's core consists of iron alloys, and its movement creates our planet's magnetic field.

Semimetals

Semimetals are elements with properties between those of metals and solid nonmetals. Examples of semimetals include arsenic (As), bismuth (Bi), and antimony (Sb). Semimetal properties differ from those of the metal group of native elements.

In nature, semimetals also occur quite rarely in pure forms. Beautiful, skeletal bismuth crystals with iridescent, rainbow-like surfaces popular at mineral shows are synthetics.

Atoms in covalent compounds like semimetals are bonded via covalent bonds rather than metallic ones. This brings some atoms closer together than others, which results in a less symmetrical structure. Consequently, covalent compounds have some physical properties that differ in different directions.

Nonmetals

The nonmetal group includes sulfur (S) and two well-known polymorphic modifications of carbon (C): graphite and diamond. The properties of nonmetal native elements differ significantly from those of the metal and semimetal groups.

Nonmetals don't have metallic lusters. For example, diamond has an adamantine or "diamond-like" luster, and sulfur's luster can appear vitreous ("glass-like"), resinous, or greasy. Covalent bonds also make nonmetals brittle instead of ductile.

Conclusion

The Nickel-Strunz classification of native elements provides a comprehensive framework for understanding the unique properties and characteristics of these naturally occurring single-element minerals and alloys. From the soft and malleable gold sub-group to the hard and dense platinum sub-group, and from the semimetals to the nonmetals, each native element class offers a fascinating glimpse into the diversity of our planet's geological wonders.

By exploring the Nickel-Strunz classification, we can gain a deeper appreciation for the intricate relationships between the elements and their natural forms, as well as the processes that shape the Earth's mineral landscape. This knowledge can inform our understanding of the formation and distribution of these valuable resources, as well as guide our responsible stewardship of these natural treasures.