Reticulation...

Mineral Matters #743

The term "reticulated" is derived from the Latin word "reticulatus" meaning "covered with a net" or "having a net-like pattern". This, in turn, comes from the Latin "reticulum" which is a diminutive of "rete" meaning "net".

In a general sense, reticulated describes something that has a net-like, web-like, or mesh-like pattern, consisting of interconnected lines, fibres, or elements that crisscross to form a network of open spaces.

When applied to minerals, "reticulated" refers to a specific growth habit or form that the mineral takes. It describes aggregates of crystals that have grown together in an intricate, interwoven, and often delicate network resembling a fine net or lace.

Key characteristics of a reticulated mineral habit are:

• A Net-like Structure: The crystals form thin, interconnected strands, blades, or needles that crisscross and intergrow, leaving open spaces between them.

• Delicate and Fragile: Due to the thinness of the individual crystals and the open nature of the structure, reticulated mineral specimens are often very delicate and easily broken.

• Often 3D: The network can extend in three dimensions, creating a complex, intricate tangle.

• Formation Conditions: This habit often forms when minerals precipitate rapidly from solution in open cavities or spaces, allowing the crystals to grow outward without being constrained by surrounding rock.

Cerussite (PbCO₃), a lead carbonate mineral, is perhaps one of the most famous and striking examples of a mineral that commonly displays a reticulated habit. It forms through cyclic twinning where the angles are multiples of 60 degrees. This commonly leads to "star-shaped" aggregates (especially "sixlings") where individual blades radiate outwards.

Below: Reticulated cerussite about 100mm wide, Broken Hill, New South Wales. Federation University Ballarat specimen.