Glass Material Samples: Lightning, Volcano, and Meteorite Formed Glass

On the fourth and topmost floor of RISD’s Metcalf Studios, in Room 401, the Glass Department has amassed a treasure-hoard of silicate-based samples for study in a long narrow vitrine. As part of the Graduate Glass Studios, the Graduate classes of ’19 & ’20 have begun to organize, catalogue, research, and write about the objects in the vitrine collection. This first installment focuses on some naturally occurring forms of glass: obsidian, fulgurites, and moldavites.

Libyan Desert glass or Great Sand Sea glass is an impactite found in areas in the eastern Sahara, in the deserts of eastern Libya and western Egypt. The myth states that its origin could be a meteorite shower, from millenia ago, that created a massive sheet of glass in the desert.

Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. Obsidian is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth.

Natural tubes, clumps, or masses of sintered, vitrified, and/or fused soil, sand, rock, organic debris and other sediments that can form when lightning discharges into ground. They can therefore be referred to as petrified lightning. They are classified as a variety of the mineraloid lechatelierite, although their absolute chemical composition is dependent on the physical and chemical properties of the usually granular-crystalline material providing an electrically and thermally conductive dissipation network for lightning-facilitated energy transfer. They are commonly hollow and/or branching assemblages of glassy, protocrystalline, and heterogeneously microcrystalline tubes, crusts, slags, vesicular masses, and clusters of refractory materials that often form during the discharge phase of lightning strikes propagating into silica-rich quartzose sand, mixed soil, clay, or other sediments. Fulgurites are homologous to Lichtenberg figures, which are the branching patterns produced on surfaces of insulators during dielectric breakdown by high-voltage discharges, such as lightning.

Moldavites were first described more than two hundred years ago. The first scientific report about these strange stones, appearing only in the south of the Czech Republic in 1786. Although its origin remains a mystery, it is connected with the fall of a huge meteorite on the earth, the impact of which created the thermal energy that melted the original rock. The pressure of the explosion then shot this melted rock to a height of about 50 kilometers, and its cooling descent back to earth’s surface gave rise to natural stones of peculiar shapes and colors.

Mays Albaik (MFA’19), Nasser Alzayani (MFA’19), Ghada Aldabbagh (MFA’20), Eli Backer (MFA’19), Karin Forslund (MFA’19), Kimberly Nguyen (MFA’20), Yufei Quan (MFA’19).