Rainbow lattice sunstone, also known as rainbow lattice, is a type of orthoclase feldspar that exhibits a rare combination of

aventurescence In gemology, aventurescence (sometimes called aventurization) is an optical reflectance effect seen in certain gems. The effect amounts to a metallic glitter, arising from minute, preferentially oriented mineral platelets within the material. Thes ...

adularescence Adularescence ( ) is an optical phenomenon that is produced in gemstones like moonstone. The optical effect is similar to labradorescence and aventurescence. Description The effect of adularescence, also commonly referred to as '' schiller'' ...

, and a distinctive

iridescence Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, butterfl ...

lattice pattern. The iridescence lattice pattern consists of inclusions that are the result of crystallographically oriented

exsolution A solid solution, a term popularly used for metals, is a homogenous mixture of two different kinds of atoms in solid state and have a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The wor ...

crystals within the

feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldsp ...

crystal. ''Sunstone'' refers to its physical appearance instead of its

chemical composition A chemical composition specifies the identity, arrangement, and ratio of the elements making up a compound. Chemical formulas can be used to describe the relative amounts of elements present in a compound. For example, the chemical formula for ...

.Lalous, G., 2018
Journal digest: Delve into the colours of rainbow lattice sunstone.Gemmological Association of Great Britain (Gem-A)
Ely Place, London, Great Britain. Rainbow lattice sunstone is produced from a remote part of the Australian desert known as the ''Mud Tank Zircon Field''. It is an area consisting of dry plains with rocky outcrops that lies in the

Harts Range Harts Range is a town in the Northern Territory of Australia located on the Plenty Highway by road northeast of Alice Springs. Most of its population are of Aboriginal descent, residing in the nearby community of Atitjere. Since 1947, each y ...

north-east of

Alice Springs Alice Springs ( aer, Mparntwe) is the third-largest town in the Northern Territory of Australia. Known as Stuart until 31 August 1933, the name Alice Springs was given by surveyor William Whitfield Mills after Alice, Lady Todd (''née'' Al ...

Northern Territory The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an states and territories of Australia, Australian territory in the central and central northern regions of Australia. The Northern Territory ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. The primary source of this sunstone is covered by a single mining claim about in size. Lower-quality Rainbow lattice sunstone is produced at another claim about away from the primary source.

Inclusions

Initially, the study of this gemstone in 1989 concluded that the inclusions were made up of

ilmenite Ilmenite is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printing ...

(for the iridescence lattice and black triangles) and

hematite Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...

(for the orange platelets). From 2017 to 2018, six samples of rainbow lattice sunstone were studied using

electron microprobe An electron microprobe (EMP), also known as an electron probe microanalyzer (EPMA) or electron micro probe analyzer (EMPA), is an analytical tool used to non-destructively determine the chemical composition of small volumes of solid materials. It ...

analysis,

X-ray diffraction X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

analysis, and laser

Raman spectroscopy Raman spectroscopy () (named after Indian physicist C. V. Raman) is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Raman sp ...

. It was found that the host mineral is orthoclase (Or₉₆Ab₄), as previously reported in the literature and the inclusions causing the aventurescence are hematite. This research also discovered that the lattice patterns consist of orangey brown platelets of hematite and the black platelets consist of

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the ...

. Hematite (Fe₂O₃) which are small mainly yellow to deep orange platelets which can be hexagonal shape and are generally in one plane within the feldspar. This effect is called ''aventurescence'' or ''sunstone effect'' which gives some of the gems an orange glow. Hematite also forms as very thin blades that occur on one plane in different directions. These blades are oriented in different directions by a process known as lamellar twinning and also displays ''sagenitic twinning'', which forms the lattice pattern. Magnetite ( Fe₃O₄) forms black, equilateral triangles. The magnetite that has no alteration is black with a metallic sheen. NT41

History

It was first discovered in late 1985 by Darren Arthur and Sonny Mason, on a small claim owned by Mason. The original source is located at what is now known as the ''Rainbow Caterpillar Mine'', in the Harts Range northeast of Alice Springs in the Northern Territory of Australia. It was identified at the GIA and declared a new gem variety in 1989.Koivula, J.I., and Karnmerling, R.C., 1989
''Gem News.'' ''Gems & Gemology.''
25(1) p.47 After Mason's death, Arthur went to co-found Asterism Gems, a company which was set up to market and sell the gemstones.

Similar sunstone

Specimens of

potassium feldspar Potassium feldspar refers to a number of minerals in the feldspar group, and containing potassium: *Orthoclase (endmember formula K Al Si3 O8), an important tectosilicate mineral that forms igneous rock *Microcline, chemically the same as orthoclas ...

that display a phenomenon remarkably similar to Rainbow lattice sunstone have been found in the area of

Statesville, North Carolina Statesville is a city in and the county seat of Iredell County, North Carolina, United States, and it is part of the Charlotte metropolitan area. Statesville was established in 1789 by an act of the North Carolina Legislature. The population was r ...

. This material contains brown and black exsolution platelets of hematite and ilmenite that show thin-film interference colors along the interface with the host feldspar. Its base colors include blue-gray, tan, and pink. Fine hematite inclusions are apparently responsible for the pink color. Very few of these potassium feldspar crystals are suitable as a gemstone because they are typically quite brittle and tend to break along cleavage during cutting. The source rock of this material is a biotite gneiss.Kunz, G.F., 1890) ''Gems and Precious Stones of North America.'' New York: Scientific Publishing Company., p. 164.Raleigh, S.C., Renfron, N., and Sun, Z., 2017
''New Phenomenal Feldspar from North Carolina With Iridescent Inclusions, G&G Micro-World.''
''Gem & Gemology.'' 53(4) pp.467-468.

External links

Mud Tank Zircon FieldDeclared fossicking areasFossicking in the Northern TerritoryNorthern Territory Government, Australia
Retrieved 2021-28-02.

ttps://www.mindat.org Minndat Organization Retrieved 2021-28-02.
5 Things to Know About Rainbow Lattice Sunstone
By Brecken Branstrator, 10X blog, NationaljewelerCom. Retrieved 2021-28-02.

References

{{reflist Feldspar