Rhodonite: Properties, Facts and Photos

Rhodonite is a pink to red manganese silicate mineral best known for its black markings caused by manganese oxides. It's mostly used for cabochons, beads, carvings, and ornamental objects rather than faceted gemstones. 

What is Rhodonite?

Rhodonite is a relatively rare mineral found in many locations around the world, but only in small quantities. Its colour varies from light pink to deep red. Stones often feature black markings caused by manganese oxides.

These can form as dendrites, which are crystals with a branching shape. The word 'dendrite' comes from the Greek 'dendron', meaning 'tree.' Dendrites often resemble organic matter.

The markings caused by manganese oxides can also occur as veins, fracture fillings, or form part of the matrix. Matrix is the host rock in which rhodonite forms.

Rhodonite forms primarily in metamorphic rocks. Once crystals have formed, exposure to oxygen can cause them to oxidise due to the presence of manganese. During this process, manganese minerals react with oxygen, producing manganese oxide minerals that are usually black.

Over time, a crust or coating of manganese oxides forms on the surface of the crystals. The crust, which can vary in thickness as it grows, can form intricate patterns, such as dendrites or veins.

An oxide is a chemical compound that contains at least one oxygen atom and one other element in its chemical composition.

Manganese minerals and manganese oxide minerals describe different chemical compounds, both of which contain manganese. Manganese minerals contain manganese as their essential component. Manganese oxide minerals are minerals where manganese is combined with oxygen.Pure rhodonite crystals that have not been oxidised can be found, but are very rare.

Although rhodonite can form individual crystals, it's more common for them to crystallise in masses. Crystals that form with a massive habit grow in a tightly intergrown, shapeless mass.

The Meaning of 'Rhodonite'

Discovered in the Ural Mountains in 1790, rhodonite was named in 1819 by German naturalist Christoph Friedrich Jasche.

The rhodonite used for lapidary purposes is typically opaque. Deep red-coloured, translucent crystals can be used for gemstones, but are rare. Although usually faceted, rhodonite is extremely difficult to cut due to its perfect cleavage in two directions.

Rhodonite is found in the United Kingdom, Brazil, Canada, Italy, India, Madagascar, South America, New Zealand, and Tanzania. The most notable locations for fine-grade crystals include the Ural Mountains (Russia), Broken Hill (Australia), and Franklin, New Jersey (USA).

The Difference Between Rhodonite and Rhodochrosite

Rhodonite and rhodochrosite are two different manganese minerals that are often confused due to their names and similar pinkish-red colour.

'Rhodochrosite' comes from the Greek 'rhodon' meaning 'rose', and 'chroma' meaning 'colour'. 'Rhodonite' also comes from the Greek word 'rhodon' because of its colour.

Rhodonite is the rarer of the two minerals.

The most significant difference is hardness. On the Mohs scale of hardness, rhodonite grades 5.5 to 6.5, while rhodochrosite grades 3.5 to 4. 

Identifying well-formed, translucent crystals of rhodochrosite and rhodonite can be more difficult on sight alone. However, material that occurs with a massive habit is much easier.

Although black markings caused by manganese oxides can occur in rhodonite and rhodochrosite, the way they form is distinctively different in both minerals.

Rhodochrosite can usually be identified by its white streaks or concentric bands, which are usually calcite.
The mineral being sold in the following photo is rhodonite, not rhodochrosite. 

Article Pictures

The rhodonite at the top of our article is courtesy of Stan Celestian.

The crystal in the second photo is courtesy of The Arkenstone.

The third photo was taken by Stone Mania during a visit to the Smithsonian National Museum of Natural History, Washington, D.C.

Pop-up photos
Rhodonite: Courtesy of Igor Schwartzmann. Dendrites: Courtesy of Captain Tenneal.