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Plasma

Material name: Plasma
Synonyms: Boskovštejn Plasma
Material (geologic): Unknown, probably replacement opal in degraded serpentinite

Nodule of Southern Moravian plasma.
Foto: Elburg/Meinel/Rummer, 2000

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General characteristics

(Page under construction)

(In part adapted from Lech 1981a)

Material: Strictly speaking, this material does not exist, if we may believe the diverse geologists we questioned on the subject. In the literature the term 'plasma' surfaces every now and then. It is mentioned twice by Luedtke: "...carnelian, plasma, heliotrope, (...) are all cherts (...) that gemdealers have valued since antiquity" (p. 63). A bit further on we learn that "the darker green of plasma" is caused by chlorite or celadonite.
The most detailed reference we found is in Lech's very thorough review of Central European raw materials. Here we get a bit further as he mentions that plasma is "... opal containing in its mass the relicts of the rock from which it originated; in this case these were serpentine marbles from the Proterozoic age." He goes further describing the honey coloured as the archaeologically most frequently used variety and christens it "the Boskovštejn plasma type", after a site near that village. The description fits well with the one our tame geologist sent us: "It sounds like a kind of 'replacement opal'. That is something that started its life as an ordinary stone and was turned into opal by the infiltration of warm, Si02-rich waters". More or less the same about its genesis is mentioned in Novák & Pfeiferová 1991, where plasma is mentioned as being a "siliceous waste", formed by the weathering of serpentinite in the Bohemian-Moravian Uplands.
After a first, unsuccessful attempt to find the stuff, which concentrated on Škorpion Hill in Southern Moravia as this site is mentioned by Lech (1981a) as a possible mining site, we found a material called 'plasma' at a stone dealer in Germany. As it looked quite spectacular (see picture below) we took another try and checked a few locations serpentinite in the same region. We found what we were looking for on the first location, although the quality can't compete with the exotic specimen.
Plasma occurs in small nodules (most we found are about 5 to 6 centimetres) with a very hard and thin white cortex, lying in the ploughed soil. It is slightly translucent and has a matte, slightly uneven fracture.
Color: Highly variable, from yellow to reddish and brown, but most nodules contain (dark) greenish material.
Other information: As it is a weathering product, it is probably wrong to speak of in situ or primary occurrences anyway, but all material we found had been dislodged from any possible parent rock and was lying in the topsoil.
Knapping notes: Poor to very poor. Even the very nice and reasonably glassy looking piece from Zimbabwe was a nightmare to knap. It requires a disproportional amount of force to detach a flake and as the fracture doesn't 'run', and you end up with a large amount of waste and a few flakes, most of which end in a step fracture. Most material from Moravia just shatters, but this could be (partly) due to frost weathering, although even very fresh looking material shows a tendency to end up in a heap of angular fragments.
Archaeological description: Not much is known about the archaeological use of plasma, but judging from its poor knapping properties it will never have been more than a local substitute.

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Slatina

Locality: Slatina, Na černém, Southern Moravia, Czech Republic
Synonyms: N/A
Geographic description: Na černém is a hill reaching 391 metres asl. directly to the west of Slatina, a village near Jevišovice, approx. 45 kilometres southwest of Brno.
Geographical co-ordinates: Lat. 49 01' 17" N
Long. 016 00' 27" E
(Mapdatum WGS 84)

Co-ordinate precision: Open county, within a dozen or so metres. Measured with a hand held GPS.
Other topographical information: To reach Slatina, you will need a reasonable map, scale 1:200.000 or larger, as it lies hidden in a maze of small roads and villages. The rough directions are: From the main road (38/E 59) from Znojmo to Moravské Budĕjovice, which is basically the road from Prague to Vienna. Near Pavlice take the 398 to the east to Jevišovice (approx. 6 km), Slatina lies another 3 kilometres to the Northeast.
Additional information: Sampling location at Slatina
Foto: Rengert Elburg, 1999
  In the picture above, you look from Na černé hill towards Slatina. The field in the foreground is our sampling site. The material is frequent at the surface, mainly at the northern side of the road.
Visitors information: In de immediate vicinity there is not much to do, but Znojmo has got a lot of places to stay, drink and eat, as long you don't mind the Austrians coming in for a cheap night of drinking. If you are prepared to drive a bit further, do go to Brno, the capital of Moravia. Although a bit sleepy, it has a huge choice of eating places, bars, wineries, and the like. There are a few inexpensive hotels in the centre, so don't be lured by the big noisy place at the railway station or the former Inter-Hotel at the west side of the centre. If in or near Brno do visit the Moravian Museum. It has very good geological and paleontological collections and a small but nice archaeological department. The staff is extremely helpful and there are English translations of their catalogues, but make sure you have enough small change to buy them.
Sampling information: As mentioned above, the material is lying at the surface to be picked up, and there seems to be an ample supply.
For a full-blown picture of sample,
click here (86 KBytes).
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Foto: Elburg/Meinel/Rummer, 2000
Sample description: Four typical pieces to show the range of colours present.

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Bojanovice

Locality: Bojanovice, Southern Moravia, Czech Republic
Synonyms: N/A
Geographic description: Bojanovice is a small village directly south of Jevišovice.
Geographical co-ordinates: Lat. 48 58' 30" N
Long. 015 59' 06" E
(Mapdatum WGS 84)

Co-ordinate precision: GPS-measured in open country, within 20 to 30 metres.
Other topographical information: See the general description for Slatina, but instead of going to the Northwest from Jevišovice, take the only road southwards. After a kilometre or so, you see a crucifix on the roadside, here we did our sampling.
Additional information: Sampling location at Bojanovice
Foto: Rengert Elburg, 1999
  Not a very aesthetic picture, but you will recognize the site immediately. As we were only passing through, we do not know how big the actual site with plasma is. It could be there is a lot more and/or better material in the neighbourhood, as the serpentinite is mapped as being nearly a square kilometre in extend.
Visitors information: See above
Sampling information: The small nodules of plasma are lying directly on the ploughed fields
Sample description: As the material of Bohanovice is exactly the same as that of Slatina, no picture in this first version.

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Plasma from Zimbabwe

Sample description: This material is very much displaced on this site, but as it is quite nice and gives off beautiful pictures, we bring it as a curiosity. According to the guy we bought it from, it comes from the Great Dyke region in Zimbabwe, but he couldn't give a more precise location.
For a full-blown picture of sample,
click here (65 KBytes).
freshly flaked plasma from Zimbabwe
Foto: Elburg/Meinel/Rummer, 2000
Transparent flake of plasma
Foto: Elburg/Meinel/Rummer, 2000
For a full-blown picture of sample,
click here (69 KBytes).
 

Last modified
December 29, 2000
Contents primarily by:
Rengert Elburg
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