Resinous luster refers to a resin-like shine or the appearance of amber, a fossilized resin organic gemstone, or how they reflect light. Some elements, gems, or minerals like sulfur, sphalerite, realgar, pyromorphite, cetineite, and other transparent to translucent nonmetallic specimens with moderately high refractive indices have this luster.
Remember, luster refers to the quality and quantity of light reflected by minerals, rocks, or crystals or how they appear in reflected light. It depends on things such as structure, refractive index, reflectivity, transparency or opaqueness, and roughness of the specimen.
Let us look more into what resinous luster is and give you some of the resinous minerals.
Hannes Grobe, CC BY-SA 2.5, via Wikimedia Commons.
What is resinous luster?
Resinous luster is a kind of luster that resembles the appearance of resin, such as the one secreted by conifer trees or something like honey. It is one of the nonmetallic luster types and a transition from subadamantine that is a bit dull but still shiny, i.e., with average or medium reflectance.
This luster is common in transparent to translucent minerals and organic gemstones whose refractive indices are moderately high but not as high as that of adamantine. Most resinous specimens are often yellowish, orange, brownish, or reddish. However, they can be colorless or have other colors.
Lastly, resinous specimens with less shine are subresinous. For instance, wilkeite, pyromorphite, fluorapatite, triphylite, and phosphosiderite, may have a subresinous to vitreous luster, while tantalite is submetallic subresinous.
Which minerals have resinous luster?
Luster kinds don’t have strict boundaries, and minerals or gemstones can have multiple types. For instance, minerals like monazite, homilite, staurolite, pyrochlore, xenotime, vesuvianite, childrenite, strontianite, epidote, microlite, willemite, holtite, and sometimes tourmaline may have a vitreous to resinous.
Similarly, minerals like atelestite, sphene, wulfenite, and vanadinite have a resinous or adamantine luster. You will also get specimens whose luster ranges from resinous to pearly, greasy, submetallic, dull, or waxy.
Here are some minerals and gemstones, including organic ones with resinous luster.
1. Amber
Amber is an organic gemstone (not a mineral) formed from fossilized tree resins, often used as a reference for resinous shine. It has a refractive index of 1.539 – 1.545, can be colorless, have inclusions, or come in various colors, including pale yellow, light to deep red, lemon yellow, yellowish brown, deep yellow, and rarely green, blue, or gray.
There are various amber gemstones, including Baltic, Burmese, Canadian, Dominican, Blue, Mexican, Oise, Rovno, and New Jersey Charentese amber, among many others. Some of their uses of amber are in jewelry (beads and cabochons), and people often use it in bracelets, earrings, necklaces, or decorative pieces.
2. Sphalerite (ZnS)
Sphalerite, zinc blende, or blende, is a valuable gemstone and an important ore of zinc that comes in various colors, including light to dark brown, yellow, red, green, reddish brown, black, or colorless.
Tis mineral has a relatively high refractive index of 2.369, and specimens tend to have a resinous luster, especially the yellow varieties. However, others may have an adamantine to greasy lusters.
3. Sulfur
Sulfur is a pale- or lemon-yellow element with atomic number 16 whose crystals have a resinous to greasy luster and a refractive index of 1.698-1.721. Some of its uses include making sulfuric acid, medicines, bleaching agents, cosmetics, rubber vulcanization, explosives, etc.
3. Realgar (As4S4 or AsS)
Realgar is a red to yellow-orange lovely gemstone with a resinous luster. It is also a minor arsenic ore that was once used in fireworks and as a pigment.
4. Pyromorphite (Pb5(PO4)3Cl)
Pyromorphite belongs to the apatite group with a resinous and sometimes greasy to subadamantine luster. It has a refractive index of 2.042 to 2.059 and comes in various colors, including shades of green, brown, tan, grayish or white, yellow-brown/orange/brown/green, yellowish-green, or colorless.
Some of its uses include as a minor lead ore and as a gem valued by collectors.
6. Cetineite ((K, Na)6Sb3+12(Sb3+S3)2O18(OH)0.5 · 5,5H2O)
Cetineite is a transparent to translucent red-orange mineral with a resinous luster that exists as tufts of elongated acicular crystals.
Besides the above, other less familiar minerals with resinous luster include metavoltine, sarabauite, sanmartinite, coalingite, and genthite.
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/
- 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.