Chalcedony and Amethist
| ID | 213 | |
|---|---|---|
| Mineral |
Chalcedony
Amethist |
|
| Location | Iraí - Rio Grande Do Sul - Brazil | |
| Fluorescence | LW-UV: close SW-UV: close |
|
| Mindat.org |
View Chalcedony information at mindat.org View Amethist information at mindat.org |
|
Mindat data
| ID | 960 |
|---|---|
| Long ID | 1:1:960:9 |
| IMA Status |
0 1 |
| Variety of | 3337 |
| Entry type | 2 |
| Description | Depending on the context, the term "chalcedony" has different meanings. 1. A more general term for all varieties of quartz that are made of microscopic or submicroscopic crystals, the so-called microcrystalline varieties of quartz. Examples are the ... |
| Other Occurrences | Very common. As nodules, vein fillings, crusts in volcanic rocks. As sinter-like crusts in low- to medium temperature hydrothermal veins. Main constituent in silica-rich marine sedimentary rocks. As nodular concretions and layers in limestones and marls. As a metasomatic replacement in limestones and marls ("replacement chert"). As cement in sandstones. Replacing other minerals in pseudomorphoses. As a fossilizing material (petrified wood, coral agate). |
| Diapheny | Translucent |
| Tenacity | brittle |
| Colour | colorless, white, gray, blue, any color due to embedded minerals, multicolored specimen not uncommon. |
| Hardness (min) | 7.0 |
| Hardness (max) | 7.0 |
| Lustre | Vitreous |
| About the name | Mentioned by Agricola (1546) of a stone named for the town of Chalcedon, now called Kadıköy, and is a district within the city of Istanbul, Turkey. |
| Streak | White |
| Crystal System | Trigonal |
| Cleavage Type | None Observed |
| Fracture type | Conchoidal,Sub-Conchoidal |
| Twinning | Quartz crystallites in the chalcedony fibers are polysynthetically twinned by the Brazil law (left- and right-handed domains). |
| UV | None in a pure specimen, however, green fluorescence in short-wave UV light is very common at many localities. |
| Comment Luster | vitreous when polished, fractured surfaces have a dull or waxy luster |
| ID | 198 |
|---|---|
| Long ID | 1:1:198:0 |
| IMA Status |
0 1 |
| Variety of | 3337 |
| Entry type | 2 |
| Description | A violet to purple variety of quartz that owes its color to gamma irradiation (Berthelot, 1906) and the presence of traces of iron built into its crystal lattice (Holden, 1925). The irradiation causes the iron Fe(+3) atoms that replace Si in the lattic... |
| Other Occurrences | Very common, in many different environments. The commercially most important occurrences are in volcanic rocks, where amethyst crystals outline former gas cavities. In low and medium temperature hydrothermal veins associated with iron ores. As late overgrowth ("scepter quartz") on quartz in pegmatite and alpine-type environments. |
| Colour | Violet - purple |
| Hardness (min) | 7.0 |
| Hardness (max) | 7.0 |
| Lustre | Vitreous |
| About the name | From Greek "a-methystos", meaning not drunk. |
| Crystal System | Trigonal |
Details
Price: € 20
Dimensions: Not registered
Weight: 234 g
Visibile in overview:
Notes:
| Symbol | Element | |
|---|---|---|
| O | Oxygen | |
| Si | Silicium |