Crisoprasa
Cuarzo is a mineral with formula SiO₂, in the Silicatos [Tectosilicatos (Grupo Cuarzo)] group. This specimen comes from Szklary, Ząbkowice Śląskie, Baja Silesia (Dolnośląskie), Frankenstein, Polonia and joined the Terrium collection in 1979.
Description
Small plate of chrysoprase with a rough, earthy-looking matrix, in a "sandwich" configuration. The green material shows a somewhat subdued tone, with soft waxy lustre and a distinct conchoidal fracture, typical of microcrystalline chalcedony. Colour slightly less saturated and more opaque than in gem-grade specimens (medium green).
About Cuarzo
Chrysoprase is the most valuable variety of the chalcedony group. Its green colour is due to inclusions of nickel silicates. Though it shares the formula of quartz (SiO₂), its structure is cryptocrystalline (a fibrous and microcrystalline aggregation).
About the locality
World reference and first documented locality for chrysoprase, worked since the Middle Ages together with nickel and other minerals, until final closure in 1980. Many spoil heaps remain in the area, though almost all are covered by very dense vegetation. They are called the "Frankenstein deposits", the historic name of the capital, associated both with the novel "The Modern Prometheus" and with a real black legend. During the 1606 plague epidemic, a group of gravediggers exhumed corpses to make a "poisonous powder" and scatter it in houses, seeking to increase their work. They were caught and burned alive. It seems very likely that Mary Shelley took inspiration from this event for her story. And by the way: Frankenstein literally means "the Franks' stone" (Franken = the Franks, Stein = stone).
Technical data
- Catalogue No.
- 0335
- Composition
- SiO₂
- Name
- Cuarzo
- Variety
- Calcedonia (Crisoprasa)
- Group
- Silicatos [Tectosilicatos (Grupo Cuarzo)]
- Category
- Meritum Persé
- Mine
- Szklary
- District / Municipality
- Ząbkowice Śląskie
- Province
- Baja Silesia (Dolnośląskie)
- Region
- Frankenstein
- Country
- Polonia
- Size (cm)
- 8.5 x 6 x 1.6
- Weight
- 85.6 g
- Acquired
- 1979
- Ex-collection
- Willfried Kittler
- Etymology
- From the Greek "chrysos" (gold) and "prason" (leek), for its green colour.
- Quality
- Buena
- Value trend
- Estable
Related specimens
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- Cristobalita — Estados Unidos
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- Cuarzo (Cloritado) — Nepal
- Cuarzo (Cloritado) — Nepal
- Cuarzo — Portugal