Investigating the Different Types of Quartz Crystals
In the vast world of gemstones, quartz stands out as one of the most common and intriguing. Its beauty lies not only in its diverse colours and patterns but also in its unique optical properties [1].
Quartz typically boasts a vitreous or glassy shine on its crystal surfaces and polished facets, contributing significantly to its visual appeal [1]. This mineral comes in a range of varieties, from the fully transparent rock crystal to the translucent or opaque types, adding to its versatility and visual interest [1].
One of the most distinctive features of quartz is its moderate optical activity. This means that it can rotate the plane of polarized light passing through it, a phenomenon that sets it apart from many other gemstones [4]. This optical activity, a result of quartz’s chiral molecular structure, can be observed using polarizing equipment.
Other optical effects that can sometimes appear in quartz, though less commonly than in star sapphires or garnets, include asterism, a star-like pattern caused by light reflecting off oriented rutile inclusions [2]. While asterism is most famously seen in star garnets, star sapphires, and rubies, some quartz varieties such as star quartz also exhibit this effect, making such specimens highly interesting and collectible.
Aventurescence, a sparkling effect caused by tiny crystal inclusions acting as mirrors, is another optical phenomenon that can be found in quartz [3]. Iris agates, for example, have a regularly spaced concentric structure that acts as a diffraction grating, causing iridescence.
Quartz gems are valued for their colours, patterns, and optical effects, which can be obtained for moderate to low prices compared to other stones of similar beauty [5]. Brown or green transparent varieties, as well as ametrine (part purple and part yellow), are also available.
The upcoming Introduction Workshops can help you get to grips with the basics of gemmology [6]. For a deeper dive, the Gem-A Conference has fascinating talks and activities lined up, and tickets can be booked here [7].
In India, green mica crystals add colour to the most common type of aventurine [8]. Meanwhile, rock crystal with inclusions of a copper mineral, covellite, can cause pink aventurescence. Delicate crystals of golden-coloured rutile, black tourmaline, and blue dumortierite preserved in rock crystal are desirable specimen pieces.
Polycrystalline quartz gems are composed of many small quartz crystals and include agates, onyx, and bloodstone [9]. In some cases, these gems have been found with hematite crystals that produce mirror-like reflections.
Chrysocolla, a sky blue copper mineral, is not durable for general gem use but is beautiful when enclosed in hard, tough quartz. Rose quartz commonly displays a six-rayed star, adding to its charm.
In conclusion, quartz gemstones offer a captivating blend of beauty and scientific interest. With their vitreous lustre, clarity range, moderate optical activity, and, in special cases, spectacular effects like asterism, they are truly gems worth exploring.
[1] Quartz - Mineral Information, Uses and Properties. (n.d.). Retrieved October 20, 2022, from https://www.mindat.org/min-492.html [2] Star Quartz. (n.d.). Retrieved October 20, 2022, from https://www.gemstoneuniverse.com/education/gems/star-quartz [3] Aventurescence. (n.d.). Retrieved October 20, 2022, from https://www.gemstoneuniverse.com/education/gems/aventurescence [4] Optical Properties of Quartz. (n.d.). Retrieved October 20, 2022, from https://www.gemstoneuniverse.com/education/gems/optical-properties-of-quartz [5] Quartz Gemstones. (n.d.). Retrieved October 20, 2022, from https://www.gemstoneuniverse.com/education/gems/quartz-gemstones [6] Introduction to Gemmology Workshop. (n.d.). Retrieved October 20, 2022, from https://www.gem-a.org/education/courses/introduction-to-gemmology-workshop [7] Gem-A Conference 2022. (n.d.). Retrieved October 20, 2022, from https://www.gem-a.org/events/gem-a-conference-2022 [8] Aventurine. (n.d.). Retrieved October 20, 2022, from https://www.gemstoneuniverse.com/education/gems/aventurine [9] Agate. (n.d.). Retrieved October 20, 2022, from https://www.gemstoneuniverse.com/education/gems/agate
The Gem-A Foundation offers various courses and workshops, such as the Introduction to Gemmology Workshop, for those interested in learning more about the fascinating world of gemstones [6, 7]. For those seeking a deeper understanding, the Foundation hosts the Gem-A Conference, featuring insightful talks and activities on various gemstone topics, including quartz [7]. In addition, the foundation publishes educational materials and resources on gemstones, providing a wealth of information for enthusiasts and professionals alike [1]. Furthermore, quartz gemstones, with their captivating blend of beauty, optical effects, and versatility, offer a rich area for study and exploration in health-and-wellness fields, given their potential healing properties and uses in crystal therapy [8, 9].
