Adamantine luster (adamantine lustre in British) is a term that describes crystals or minerals, including gemstones with a very brilliant, sparkly, and highly shiny appearance, like diamonds.
Besides diamonds, other adamantine minerals include pyrargyrite, anglesite, phosgenite, tausonite, alamosite, moissanite, cassiterite, zircon, and dermatoid garnet. However, some may show some variation to other luster types or kinds.
If a mineral has less brilliance and shine but is still more brilliant than vitreous or resinous, its luster is subadamantine. Examples include austinite, stolzite, and zincite.
Let us discuss more subadamantine and adamantine luster and give you examples of minerals that have it besides diamond.
What is adamantine luster?
Adamantine luster is brilliant, sparkly, and shiny luster like that of polished diamonds. Minerals with adamantine luster are transparent to translucent nonmetals that are highly reflective and have a high refractive index, i.e., at least 1.9 or one comparable to diamonds which is 2.42. These minerals include those with heavy ions like mercury, uranium, or silver.
The term adamantine comes from the Latin and Greek word adamas, meaning hard, unconquerable, invisible, inflexible, unbreakable, or indestructible. It often refers to the hardness of diamonds, similar minerals, or even their luster.
Since luster is a quantitative measure of light reflecting the degree of minerals, rocks, or crystals, specimens with a metallic luster, like polished hematite, galena, magnetite, silver, or pyrite, have the highest luster degree often described as splendent. It resembles looking into a mirror.
These minerals are highly reflective and opaque, with non-polished ones reflecting at least 20% of the light that strikes their surface and polished more than 50%. Those that reflect less than 20% are submetallic and are a transition to adamantine.
On the other hand, adamantine is the most sparkly and brilliant luster among transparent and translucent non-metallic minerals. Minerals with this luster reflect the highest light but are less reflective than metallic luster specimens. Adamantane’s extraordinary and sparkly brilliance may resemble but exceed glassy or vitreous luster, i.e., the shine of freshly broken glass such as that seen in quartz or even resinous.
Subadamantine
Minerals, gemstones, or crystals with a luster lower than adamantine but higher than resinous have subadamantine luster. Such minerals are still more brilliant than vitreous and resinous but are a bit duller than adamantine, i.e., they lie between adamantine and resinous.
Some minerals with subadamantine luster include austinite, stolzite, tellurite, ludlockite, arsendescloizite, paralaurionite, postite, welshite, and bismite. Also, some minerals like linarite, wulfenite, zincite, torbernite, and scheelite may have a subadamantine luster that may vary to metallic, adamantine, greasy, etc.
Adamantine luster examples
Only a small percentage of minerals, i.e., less than 10%, have the adamantine luster. Most of these will show variations like adamantine/subadamantine to metallic, submetallic, resinous, vitreous, greasy, earthly, etc.
For instance, perovskite, cuprite, bronzite, and bismutotantalite have adamantine to submetallic luster, and anatase, pyrargyrite, scheelite, and stibnite have adamantine to metallic. Similarly, rhodizite, epidote, crocoite, and colemanite are vitreous to adamantine.
This variation is a normal observation as there are no strict boundaries between the various kinds of lusters. Also, some same specimens show such variations. Therefore, you have a general idea of why you may find some minerals listed differently by different authors.
Some of the minerals with adamantine luster include the following:
1. Diamonds
Diamond is pure carbon solid with crystals arranged in a cubic diamond structure whose polished luster is the reference of adamantine. However, it may be adamantine to greasy and has a refractive index of 2.418.
Besides their brilliance or sparkle, diamonds have the optical fire effect and are the hardest known natural substance in Vickers and Mohs hardness scales.
Diamonds’ common colors are brown, gray, and yellow to colorless but may be blue, black, green, violet, pink, purple, orange, translucent white, or red. Their uses include jewelry, dental and drill bits, stone cutting wheels, heat skins, and engraving. Also, it has applications in automotive, medicine, beauty, etc.
2. Pyrargyrite and proustite (Ag3SbS3)
Pyrargyrite (ruby silver or dark red silver) is a deep red sulfosalt mineral, while its isomorphous proustite is scarlet-vermilion. They both have an adamantine luster; their respective index is 2.881-3.084 and 2.792 – 3.088. respectively.
3. Tausonite (SrTiO3)
Tausonite (strontium titanate) is a red, deep red, ruby red, gray, or brownish red mineral in the perovskite group with a synthetic form called fabulite. This rare mineral has a high refractive index of 2.409 and an adamantine luster. Some of its uses include radioisotope thermoelectric generators.
4. Phosgenite (cromfordite) (PbCl)2CO3
Phosgenite is yellow-brown, yellowish gray, colorless, smoky violet or brown, and pale yellow, brown, rose, or green mineral with a refractive index of 2.40 and adamantine luster.
5. Alamosite (Pb12Si12O36)
Alamosite is a colorless, white, cream, or light transparent to translucent mineral with an adamantine luster and a refractive index of 2.188-2.145 from Alamos, Mexico.
6. Demantoid garnet
Dematoid is a green gemstone with an adamantine shine and a refractive index of 1.880–1.889. It is a variety of mineral andradite.
7. Anglesite (PbSO4)
Anglesite is colorless to white, often with a gray tint, orange, green, yellow, or blue with an adamantine and sometimes resinous to vitreous luster like cerussite. Its refractive index is 1.878 – 1.895, and some of its uses are in battery, ammunition, plumbing, radiation, X-ray shields, absorbing sound, lead ore, etc.
8. Moissanite (SiC)
Moissanite (silicon carbide) is a hard (Mohs hardness of 9.5) mineral with a refractive index of 2.65 to 2.69 and an adamantine to metallic luster. This mainly green, blue-green, emerald-green, blue-black, black, or deep blue has jewelry and commercial and industrial uses. These uses include sandblasting, grinding, honing, waterjet cutting, etc.
9. Cassiterite (SnO2)
Cassiterite is a brownish to almost black mineral and is the most important tin ore with an adamantine or adamantine metallic luster, sometimes greasy on fractures. It has a reflective index of 1.990 – 2.101, and its structure resembles rutile and often has tantalum, niobium, and a considerable amount of ferric iron or ferrous.
Cassiterite is common in igneous rock like granite, microgranites, or acidic, including granite pegmatites, skarns, and high-temperature hydrothermal veins.
10. Zircon or zirconium silicate (ZrSiO4)
Zircon is a reddish-brown, yellow, blue, green, or colorless gemstone and a zirconium source. It has an adamantine, subadamantine, and sometimes vitreous luster and a refractive index of 1.93-1.987. However, its metamict form is greasy.
It is one of the accessory minerals in metamorphic and igneous rock, with large crystals in pegmatites and carbonatites.
We didn’t exhaust the list. There are many more. For instance, some, like anatase, have a more strongly adamantine or metallic-adamantine luster, and cinnabar is adamantine to dull.
Frequently asked questions
The most familiar mineral with adamantine luster is diamond. Other less familiar ones are tausonite, zircon, phosgenite, demantoid garnet, anglesite, and pyrargyrite.
No. Sapphire, a precious mineral or gemstone, a member of the corundum mineral, has a vitreous or glassy luster.
References
- Manutchehr-Danai, M. (2009). Dictionary of gems and gemology (3rd ed.). Springer.
- Anthony, J. W., Bideaux, R, A, Bladh, K. W., & Nichols, N. C., (Eds.) (2022). Handbook of mineralogy, Mineralogical Society of America, Chantilly, VA 20151-1110, USA. http://www.handbookofmineralogy.org/
- Deer, W. A., Howie, R. A., & Zussman, J. (2013). An introduction to the rock-forming minerals (3rd ed.). The Mineralogical Society.
- Okrusch, M., & Frimmel, H. (2020). Mineralogy: An introduction to minerals, rocks, and mineral deposits. Springer. https://doi.org/10.1007/978-3-662-57316-7
- Nesse, W. D. (2018). Introduction to mineralogy (3rd ed.). Oxford University Press.