Amatista levísima
Cuarzo is a mineral with formula SiO2, in the Silicatos [Tectosilicatos (Grupo Cuarzo)] group. This specimen comes from Transvaal, Sudáfrica and joined the Terrium collection in 1850.
Description
Geode in a brown flint nodule, lined by transparent quartz crystals with a faint amethyst tint. Intense vitreous lustre and good crystal development, in sharp contrast with the opaque matrix rind; shows a white response under UV light.
History of this specimen
Historic piece. It belonged to the Bally Museum of Schönenwerd (Switzerland, 19th–20th centuries), one of the most significant private natural-history cabinets of its time, founded by the Bally family of shoe manufacturers. It later passed to the collection of Dr. Kürschner. The original label includes both references and the piece retains the number "10217" written with the typical old dip-pen ink. I now look after it in my own cabinet of mineralogical curiosities.
About Cuarzo
Quartz is the most abundant silicate in the crust; in geodes it lines cavities with well-formed crystals. Association with flint (a sedimentary microquartz variety) provides a textural contrast much valued in classical collections.
About the locality
The regional division dates from the colonial period. The referenced province, Transvaal (1885), no longer exists. It covered territories that today form part of North West, Gauteng, Mpumalanga and Limpopo. The region is geologically rich, with sedimentary and volcano-sedimentary rocks that host siliceous nodules. When fractured, these nodules reveal cavities lined by quartz, sometimes with an amethyst tint. As early as the 17th century, during the Dutch colonial period, amethyst extraction was documented in South Africa, which makes this type of specimen part of a long mining and collecting tradition.
Technical data
- Catalogue No.
- 0177
- Composition
- SiO2
- Name
- Cuarzo
- Variety
- Amatista levísima
- Group
- Silicatos [Tectosilicatos (Grupo Cuarzo)]
- Category
- Cavella
- Matrix
- Nódulo de jaspe o sílex
- District / Municipality
- Transvaal
- Country
- Sudáfrica
- Size (cm)
- 7.5 x 7 x 4
- Weight
- 190 g
- Acquired
- 1850
- Ex-collection
- Museo Bally de Schönenwerd → Dr. Kürschner
- Etymology
- From German "Quarz", of uncertain origin; "jasper" from Greek "iaspis" ("spotted stone").
- Quality
- Muy buena
- Value trend
- Al alza
Related specimens
- Cristobalita — Estados Unidos
- Cuarzo — Madagascar
- Cuarzo (Ahumado) — Namibia
- Amatista — Kazajistán
- Cuarzo (Cloritado) — Nepal
- Cuarzo (Cloritado) — Nepal
- Cuarzo — Portugal
- Crisoprasa — Polonia