Gemstone and Mineral Encyclopedia: Insight into Selenite
In the realm of gemstones, selenite stands out for its unique properties and rich history. This colorless variety of gypsum, not containing selenium, was first named by the Swedish scientist J.G. Wallerius in his 1747 book Mineralogia, eller Mineralriket.
Selenite crystallizes in the monoclinic system, often forming tabular crystals with a rhombus shape. These crystals are known for their brittle nature, tending to break along their structural planes. Despite this, selenite is not suitable for faceting but can be carved as cabochons or beads, showcasing its beauty in various forms.
The specimen of selenite in the Gem-A Gems & Mineral Collection exhibits a green hue due to copper-based mineral inclusions, adding a touch of colour to this otherwise clear gemstone. This green tint is reminiscent of the green copper carbonate mineral, malachite, which Wallerius also documented in the same year.
Selenite is found in sedimentary rocks, specifically limestone, and is formed by hydrothermal fluids from the magma chamber situated below. This process has led to the formation of some truly awe-inspiring selenite crystals, such as those found in the Cave of Crystals in the Naica mine in Chihuahua, Mexico, where the world's largest known crystals of selenite reside, measuring up to 1.2m in diameter and 15m in length.
The history of selenite extends far beyond its geological formation. In Roman antiquity, transparent selenite was used as window panes before the invention of glass panes. Its use continued in the Middle-Ages, where selenite was discovered in abundance in Germany in the region of Gotha and was used as substitute glass panes to protect pictures of the Virgin Mary, earning the name Marienglas.
In Roman times, selenite was also used in the Circus Maximus to create a glittering, sparkling effect during races by scattering powdered selenite on the ground. Plinius the Elder referred to selenite as specularis lapis or 'mirror-like stone', a testament to its reflective properties.
J.G. Wallerius, a professor of medicine and chemistry, and a mining specialist, made significant contributions to the field of mineralogy. His early formal identification and description of minerals, including selenite, laid the groundwork for mineralogical studies in Sweden and beyond. His documentation of malachite in 1747 is particularly noted as it helped distinguish this green copper carbonate mineral in scientific literature, marking an important step in the mineral's study and recognition.
Today, members of Gem-A can delve deeper into the fascinating world of gemstones and mineralogy through the organisation's magazines, Gems&Jewellery and The Journal of Gemmology, as well as a range of workshops and courses designed to develop one's passion for gemmology.
This article was originally posted on 18-04-2019, offering a glimpse into the past and present of selenite, a gemstone with a rich history and unique properties. Selenite was named after Selene, the Greek goddess of the Moon, due to its moon-like reflection, a fitting name for this captivating gemstone.
1) In addition to selenite, J.G. Wallerius also documented malachite, a green copper carbonate mineral, in his 1747 book.2) Selenite's name is derived from Selene, the Greek goddess of the Moon, reflecting its moon-like reflection.3) Beyond its geological formation, selenite has a history that extends into Roman antiquity, where it was used as window panes before glass was invented and even as a sparkling, glittering effect during races in the Circus Maximus.4) Today, anyone with a passion for gemmology can deepen their understanding through Gem-A's magazines, workshops, and courses.5) Members of Gem-A can explore the world of education and self-development, not limited to lifestyle, technology, entertainment, science, medical-conditions, space-and-astronomy, and of course, gemmology and mineralogy.
