Rainbow lattice sunstone, also known as rainbow lattice, is a type of

orthoclase feldspar Orthoclase, or orthoclase feldspar (endmember formula K Al Si3 O8), is an important tectosilicate mineral which forms igneous rock. The name is from the Ancient Greek for "straight fracture", because its two cleavage planes are at right angles t ...

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. The ...

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'' o ...

, and a distinctive

iridescence Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear gradually to change colour as the angle of view or the angle of illumination changes. Iridescence is caused by wave interference of light in microstru ...

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 homogeneous mixture of two compounds in solid state and having a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The word "solution" ...

crystals within the

feldspar Feldspar ( ; sometimes spelled felspar) is 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 ''plagiocl ...

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

chemical composition A chemical composition specifies the identity, arrangement, and ratio of the chemical elements making up a compound by way of chemical and atomic bonds. Chemical formulas can be used to describe the relative amounts of elements present in a com ...

.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, officially registered as Hart Range, is a town in the Northern Territory of Australia located on the Plenty Highway by road northeast of Alice Springs. It is also the name of a mountain range, after which it was named. It has also ...

north-east of

Alice Springs Alice Springs () is a town in the Northern Territory, Australia; it is the third-largest settlement after Darwin, Northern Territory, Darwin and Palmerston, Northern Territory, Palmerston. The name Alice Springs was given by surveyor William ...

Northern Territory The Northern Territory (abbreviated as NT; known formally as the Northern Territory of Australia and informally as the Territory) is an states and territories of Australia, Australian internal territory in the central and central-northern regi ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

. 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, printi ...

(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. I ...

analysis,

X-ray diffraction X-ray diffraction is a generic term for phenomena associated with changes in the direction of X-ray beams due to interactions with the electrons around atoms. It occurs due to elastic scattering, when there is no change in the energy of the waves. ...

analysis, and laser

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

. 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 . It is one of the iron oxide, oxides of iron, and is ferrimagnetism, ferrimagnetic; it is attracted to a magnet and can be magnetization, magnetized to become a ...

. 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.

History

Rainbow lattice sunstone 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

northeast of

in the

Northern Territory of Australia The Northern Territory (abbreviated as NT; known formally as the Northern Territory of Australia and informally as the Territory) is an states and territories of Australia, Australian internal territory in the central and central-northern regi ...

. 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 that contain large amounts of potassium in the crystal lattice. *Orthoclase (endmember formula K Al Si3 O8), an important tectosilicate mineral that forms igneous rock *Microcl ...

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 Iredell County, North Carolina, United States, and its county seat. The population was 28,419 at the time of the 2020 census. Statesville was established in 1789 by an act of the North Carolina Legislature. It is part ...

.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. 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.

References

{{reflist

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. Feldspar