Obsidian – Brehov, Slovakia

Eastern Slovak obsidian

General

Obsidian is a type of volcanic glass, a rock that is formed as a result of magmatic activity when hot lava comes into rapid contact with a cold environment and then solidifies rapidly. The rock is very rich in silica compounds and is a natural form of glass. It is typically dark in colour, ranging from black, grey or red. It is usually opaque, but its transparency increases as the iron oxide content decreases.

History

The occurrence of obsidian in Slovakia is relatively small compared to other local neovolcanics. Our ancestors used it to make cutting tools as early as the Palaeolithic (2 500 000 years ago), but it has been shown that these tools were also used during the Neolithic (5 000 years ago). In Europe, there are only a limited number of primary occurrences of obsidian suitable for the production of cutting tools, mainly scrapers, spearheads or knives. It is clear from the results of ongoing research that the importance of Eastern Slovak obsidian as a raw material for the production of chipped tools has far exceeded its local significance. Therefore, Eastern Slovak obsidian was distributed throughout Central and Eastern Europe and across the Balkans to the Mediterranean.

A little chemistry

Obsidian is the product of highly acidic lavas of Neogene volcanism. Their origin is closely linked to rhyolite volcanism. Its occurrences form the peripheral parts of larger volcanic bodies, mainly composed of rhyolite. The nests of obsidian nodules, incorrectly referred to by collectors as mounds, are usually found in rhyolite tuffs, from where it often weathered as a more resistant material, and therefore today its shape and surface (sculpture) often resembles Bohemian Moldavite.

The obsidian of Eastern Slovakia belongs to a group of unaltered acid volcanic glasses with a silica (SiO2) content of about 80%. The higher acidity of the local lavas has caused the obsidians to have a higher SiO2 content and a lower water content than the world average. This is the reason for their greater durability and suitability for the production of chipped tools. The water content of obsidian is unusually low. The H2O content varies between 0,19 and 0,31 %. The density varies between 2,3 and 2,4 g/cm³. Porosity is well below 1 %, and hardness is between 5 and 5,5 on the Mohs scale.

The local obsidian is transparent. Depending on its chemical composition, its colours range from black, to grey, to bluish and greenish, sometimes with silvery highlights. No other obsidian in the world offers such a colour spectrum!

Interesting / Potential

As chance would have it, the occurrence of obsidian in Slovakia dates back 15,000,000 years ago, around the same time as its Czech "brother", moldavite, to which it is often compared for its appearance, and at a certain distance and under the right light they are indistinguishable from each other. But of course on closer examination the differences are clear and there can be no confusion.

Interest in obsidians in general is growing both in Europe and worldwide. The Slovak ones are enhanced by their rare occurrence, limited quantity, unique colour and the aforementioned resemblance to Moldavites. Its current low price makes it an ideal stone for future value appreciation.

Obsidian is easy to work and polish, and as a raw material it is truly suitable for jewellery and haberdashery purposes. It is also used to make replicas of Palaeolithic cutting tools, stone beads and jewellery. Obsidian can be collected at individual sites in the form of small boulders from 1 to about 20 cm in diameter. However, most of the mounds are between 1 and 5 cm. Their predominant colour is black or blackish grey. The cut stones achieve a high polish and the cut yield is comparable to commercial coloured chalcedony.

It can be used not only in the form of plain cabochon cuts or tables, but since it is transparent, it can also be faceted in the form of rout and step cuts. Faceted stones are very spectacular and surpass in appearance the dark gneisses and morions. Due to its easy workability, it is also a suitable raw material for plastic cutting of small figures, so-called glyptics.

In any case, it deserves to be promoted as one of the very interesting materials used since the Stone Age. Although interest in natural glass is growing mainly thanks to tektites, the others are also being mentioned alongside them. The scientific community has organised several conferences dedicated to natural glass research. In 1987, one of them was held under the auspices of Charles University in Prague. For this conference, silver jewellery was produced by the Granat cooperative in Turnov, the dominant stone of which was obsidian from Eastern Slovakia. Inquiries and orders from abroad continued for several years.

Uses of obsidian

Obsidian has a wide range of uses due to its physical properties and aesthetic qualities.

1. Tools: Historically, obsidian was widely used to make various tools and weapons, especially in prehistoric times. The sharp edges of obsidian were ideal for making:

   • Arrowheads and spear points: Due to its sharpness and hardness, obsidian was an ideal material for arrowheads and spear points
   • Knives and scrapers: It was used to make cutting tools that were essential for the daily life of prehistoric people

2. Jewelry and decorative items: Due to its luster and aesthetic properties, Slovak obsidian is a popular material for making jewelry and decorative items:

   • Necklaces, bracelets, rings: Obsidian is often used in jewelry making to create various types of jewelry
   • Amulets and talismans: For its beauty and supposed protective properties, obsidian is often crafted into amulets and talismans
   • Decorative figurines and items: Handcrafted decorative items and figurines made of obsidian are valued for their aesthetic and artistic qualities

3. Healing and esotericism: Obsidian is often associated with various spiritual and healing practices:

   • Protective properties: Some people believe that obsidian has the ability to ward off negative energy and protect the wearer from psychic attacks
   • Healing: In alternative medicine, obsidian is used for its supposed abilities to promote emotional healing and balance

4. Collecting:

   • Mineral collections: Obsidian is popular among collectors of minerals and gemstones who appreciate its unique properties and appearance

5. Modern medicine:

   • Surgical scalpels: Although less common, some surgical scalpels are made from obsidian because its extremely sharp edges allow for very precise cuts

6. Sculpture making:

   • Sculpture and carving: Artists use obsidian to create detailed sculptures and carvings thanks to its ability to be finely worked