Quartz can have several phenomena including phantom crystals, rainbows or asterism (star effect).
In Part 1 of my All About Macrocrystalline Quartz series we discussed the basics of Macrocrystalline Quartz: science, nomenclature, varieties, and uses.
If you missed it or would like to review the information, check it out All About Quartz Part 1 here!
As promised in Part 2 we will be discussing Quartz crystal phenomena and inclusions present in Quartz crystals.
Phenomena is described as facts or situations that are observed to exist or happen, especially ones whose cause or explanation is in question and a Phenomenon (singular) is a remarkable person, thing, or event. And Quartz crystals have many effects that match those descriptions!
Their causes can range from inclusions to internal structures and interference, to reflection and refraction.
Inclusions are quite literally things trapped or “included” inside a crystal. Inclusions can be a solid, such as another mineral or a fragment of one enclosed within the crystal; or a cavity enclosed in a crystal that may also contain a gas, a liquid, or even a crystal; or even a flaw, fracture or an "optical illusion" which is enclosed within a crystal.
There are basically 3 types of inclusions: Antegenic Inclusions are formed before the Host Crystal and then were incased in the crystal, Syngenetic Inclusions are formed at the same time as the Host Crystal and Epigenetic Inclusions are formed in cracks or fissures after the Host Crystal formed.
The most common mineral inclusions are Chlorite (green or lavender), Hematite (red/red sparkles), Goethite (orange yellow), Rutile (golden needles), Clay (brown), Mica (dark hexagon), Specular Hematite (dark flakes, sparkle), Epidote (green needles), Tourmaline (black needles), liquid or gasses (bubbles) and Native Gold or Native Silver.
Sometimes the inclusions are so plentiful that a clear crystal will appear opaque, as with Milky Quartz.
Different Included Quartzes are known in the trade by many names: Rutilated Quartz, Tourmalinated Quartz, Lodalite or Lodolite, Garden Quartz, Scenic Quartz, Manifestation Quartz and Landscape Quartz to name just a few.
In addition, the shape of the inclusion is often named. For Instance; “Dendrites” are very thin tree like inclusions of iron, manganese, or other metallic oxides that grow in a natural fracture. A "Sagenite" is an acicular rutile, tourmaline, goethite, actinolite, or other mineral that occurs in reticulated forms. “Sagenitic” is needles or plates intersecting in a grid-like or grill-like manner. A “Needle” is an elongated crystal tapering to a fine point on each end.
Sheen is the effect caused by reflection of light from below the surface of the gemstone (whereas luster is on the surface). Below are several types of quartz sheen phenomenon:
Asterism or star shaped effect is caused by reflection off of needle-like inclusions. However, the inclusions are arranged in different directions causing several streaks of light on the surface of the stone in a star effect. Usually the inclusions which cause the stars are orientated parallel to the crystal faces. The stars can be 4, 6, or 12-pointed.
Adularescence is an “inner glow” of a gemstone. Adularescence is also known as Schiller. When light seems to emanate from within the gemstone, this phenomenon is called adularescence. Moonstone, or adularia as it is also known (hence the name), presents the best example of adularescence. The sheen will travel across the surface of the crystal when the stone is turned. Some quartz shows adularescence, but when adularescence occurs in non-adularia gemstones it is often called the "girasol effect". Due to inclusions in quartz, the effect is displayed differently than in Moonstone. As an optical phenomenon, adularescence exists only in the presence of light; it is a product of the interaction between light and the internal microstructures of the crystal. The effect is produced because of light interference caused by the light having to weave its way through the layers of the crystal with slightly different optical properties.
Iridescence is a rainbow-like play of color that changes with movement of the crystal. Naturally iridescent quartz has been recognized for more than a century and is known by many names: iris quartz, rainbow quartz, schiller quartz, anandalite, and adularescent quartz. Most Iridescent Quartz comes from India, but it has been found in other locations. Specimens have been produced artificially through the deposition of thin films of various metals (as with “aurora quartz”). It is believed natural iridescence is caused by a combination of reflective interference from surface grooving and an underlying lamellar structure, which together create a diffraction grating for visible light.
Rainbow Quartz Crystals come in two different types. The first type of rainbows may be caused by fractures within the stone that causes a prismatic effect, and exhibits lovely rainbows. The second type of Rainbow Quartz are crystals that have inclusions of rhodium, which allows them to exhibit lovely rainbow areas on the surface of the stones, rather than within them.
Other interesting types of Quartz phenomena include:
Negative Crystal is actually the term for a cavity enclosed by crystal faces in the crystal. Such a cavity may be of a completely irregular form, or it may be a regular form and look like another crystal incased in the larger one. Negative crystals are always oriented parallel to the host crystal.
Enhydros- During the process of formation of some crystals, water (or other liquids) can be trapped in bubbles in cavities inside. If the cavity is not totally filled these bubbles will move around inside. In Quartz the correct term for this is a fluid inclusion. However, you will often see this phenomenon labeled as an enhydro. Enhydros are actually formed in chalcedonies (microcrystalline quartzes). Unlike fluid inclusions, the chalcedony shell is permeable, allowing water to enter and exit the cavity very slowly. Unlike in fluid inclusions, he water inside of an enhydro agate is usually not the same water as when the formation occurred.
Phantoms are where one can see within the crystal, one or more "ghost images" which more or less resemble the external shape of the Crystal. In this case the Crystal grew to a certain stage and then stopped and then started growing again, enclosing the previous outer surfaces of that crystal. During that stop and start process those preexisting surfaces will usually receive a very fine "coating" of another substance. Making them visible once overgrown by the host crystal. Minor changes in the internal structure and/or chemical composition of a crystal can result in Color Zoning of the Crystal.
Triboluminescence - Triboluminescence is a flash of light produced when a material is subjected to friction, impact or breakage. This phenomenon often occurs when two quartz crystals are stricken together and sometimes when quartz is being cut. Triboluminescence is common in minerals. Triboluminescence is present in quartz; however, the strength of the phenomenon varies from specimen to specimen. Scientists believe the light results from a recombination of electrical charges that become separated when crystals are fractured. When the charges get back together, the air is ionized, producing a flash of light.
In my next blog I will try to explore the very complicated world of Macrocrystalline Quartz formations-both from a scientific view and from a metaphysical view!
In the meantime, please explore our great selection of Quartz here.
You can also find more Quartz available in our Etsy shop here!