Crystals, rocks, or minerals with a waxy luster have a shine that resembles that of a wax candle. Examples include turquoise, evenkite, shannonite, uranospinite, and schlossmacherite. Others like jadeite, chalcedony, and variscite will mainly show this luster but often occur with other kinds, too.
Remember, luster is the qualitative and quantitative measure of light reflected by minerals, crystals, or even rocks. It tells you how they will appear under reflected light. To describe the resultant appearance, we use descriptive words like metallic, submetallic, or non-metallic terms such as vitreous, waxy, resinous, pearly, dull or earthy, adamantine, greasy, etc.
This discussion will look more into waxy luster, including its meaning, and give you mineral examples. We also have some minerals that have this and other kinds of lusters.
What is a waxy luster?
Waxy luster describes crystals or minerals that reflect light or appear like candles, beeswax, or paraffin blocks/pieces. Their shine is moderate or soft, i.e., they reflect a below-medium light and is more matte than greasy luster. However, it is not as dull as the earthy minerals.
Waxy minerals are semi-transparent to translucent, with most having a tiny mineral aggregate that scatter light, producing this appearance. Most of these minerals will improve their appearance and bring out their color better if given a good polish.
Examples of minerals with a waxy luster
Some minerals with a waxy luster include turquoise, shannonite, evenkite, schlossmacherite, wax opal, and uranospinite. However, schlossmacherite may, at times, be vitreous.
Chalcedony, semi-transparent to translucent microcrystalline to cryptocrystalline quartz, is often waxy but can be vitreous, greasy, silky, or dull. Similarly, serpentine, especially the yellow or yellow-green variety, is waxy.
1. Turquoise
Turquoise (CuAl6(PO4)4(OH)8·4H2O) is a turquoise, bluish or blue-green mineral with a waxy luster, a Mohs scale hardness of 5-6, and a refractive index of 1.61 – 1.65 used in making rings, bracelets, buckles, or any other place with little abrasion risk.
2. Evenkite
Evenkite is a colorless to yellowish, transparent, crystalline hydrocarbon waxy mineral. This rare hydrocarbon is a main constituent of paraffin wax, has a Mohs hardness scale of 1, and is mined from Lower Evenkiysky District in Russia.
Minerals with waxy and other lusters
Luster is an important optical property of minerals and crystals. However, it lacks clear-cut boundaries, making it subjective. Also, some specimens of minerals will show several kinds.
For instance, minerals like agate, variscite, smithsonite, vanalite, leonite, beidellite, jadeite, and ravatite have a vitreous to waxy luster, while glauberite, brucite, uranophane, and pyroaurite are vitreous, pearly to waxy.
Others like hectorite, palygorskite, moolooite, and montanite may be waxy to dull or earthy, while barbertonite is waxy to pearly, weeksite waxy to silky, and chrysoprase waxy to greasy. Steatite (soapstone) and stichtite are waxy to pearly or greasy, while lizardite is resinous, waxy, or oily).
From this observation, you can confirm that luster isn’t a diagnostic mineral property. However, it can help you narrow down the possible minerals, and when used with other properties, you can easily identify unknown minerals.
- 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/
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