Parasymplesite
Chemical formula: Fe<sup>2+</sup><sub>3</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>·8H<sub>2</sub>O
Hydrated iron(II) arsenate, forming characteristic fan-like aggregates of green or blue-green acicular crystals.
Description
## Characteristics Parasymplesite is a mineral from the vivianite group, chemically a hydrated iron(II) arsenate. Its most typical form of occurrence is aggregates of radially diverging crystals, which form fan-like, spherical, or stellate clusters. Individual crystals are elongated, flattened blades or needles. This mineral is valued for its attractive, vibrant color, which draws the attention of collectors. ## Physical Properties Parasymplesite is a very soft mineral, with a hardness of only 2 on the Mohs scale, meaning it can be scratched with a fingernail. It is relatively light, with a density of approximately 3.01 g/cm³. Crystals can be transparent to translucent, and their luster is most often vitreous, sometimes pearly on cleavage planes. ## Colors and Varieties This mineral occurs in various shades of green and blue. The most common colors range from emerald green, through blue-green, to yellowish-green. Some specimens may darken over time due to light exposure or oxidation processes, similar to other minerals in its group. There are no named color varieties or commercial varieties. ## History and Name The name parasymplesite comes from the Greek word *para* (παρά), meaning "near" or "beside," and the name of the mineral symplesite. It refers to the fact that both minerals have the same chemical composition (they are polymorphs) but differ in crystal structure. Parasymplesite crystallizes in the monoclinic system, while symplesite crystallizes in the triclinic system. ## Uses Due to its rarity, low hardness, and toxic chemical composition (arsenic content), parasymplesite has no industrial applications. It is solely an object of interest for mineral collectors.
Diagnostic features
## Identification The key diagnostic feature of parasymplesite is its characteristic habit in the form of radial, fan-like aggregates of green or blue-green color. Very low hardness (2 on the Mohs scale) and a bluish-white streak are also important indicators. Occurrence in association with other secondary arsenic minerals in oxidation zones is a strong clue. ## Distinguishing from Similar Minerals - **Symplesite**: It is extremely similar and often impossible to distinguish without advanced analysis (e.g., X-ray diffraction). The main difference lies in the crystallographic system (symplesite is triclinic, parasymplesite is monoclinic). - **Vivianite**: This is a phosphate, not an arsenate. It often has a bluer color and darkens more intensely when exposed to light, becoming almost black. Chemical tests for the presence of arsenic or phosphorus allow them to be distinguished. - **Annabergite**: This is nickel arsenate, which usually has a brighter, apple-green hue. ## Crystal Forms Crystals are elongated in the form of blades or needles, often flattened. They almost always occur in characteristic radial, fan-like, stellate, or spherulitic aggregates. Less commonly, it forms crusts and coatings.
Geological environment
## Genesis Parasymplesite is a secondary mineral, formed in the oxidation zones (so-called iron caps) of hydrothermal ore deposits. It forms as a result of weathering and alteration of primary arsenic and iron-bearing minerals, such as arsenopyrite or löllingite. ## Mineral Associations It most often co-occurs with the minerals from which it forms (arsenopyrite, löllingite), as well as with other secondary arsenates, such as scorodite, pharmacosiderite, and especially with its polymorph – symplesite. Quartz, pyrite, and other sulfides may also accompany it. ## Localities Among the most important and classic localities from which renowned specimens of parasymplesite originate are historical deposits in Saxony, Germany (e.g., Oelsnitz, Schneeberg). Excellent specimens were also found in the Kiura mine in Oita Prefecture, Japan. Other known occurrences include Laurion in Greece, Bou Azzer in Morocco, and some localities in the United States.
Rarity
Uncommon
Collector aspects
## Quality Criteria The most highly prized parasymplesite specimens are those that display well-formed, large, and distinct radial aggregates on a contrasting rock matrix. An intense, vibrant blue-green or emerald color significantly increases its value. The transparency of the crystals and the absence of mechanical damage are also important. Specimens from classic, historical localities are particularly sought after. ## Popular Localities Specimens from the Kiura mine in Japan are considered the most desirable by collectors, renowned for their excellent form and color. Samples from classic German localities in Saxony, such as Schneeberg or Oelsnitz, also hold great historical and aesthetic value.
Care and storage
## Cleaning Parasymplesite is extremely soft and delicate. It should be cleaned very carefully, only dry, using a soft brush to remove dust. Due to its chemical composition, contact with water is not recommended. Ultrasonic cleaners are absolutely forbidden. ## What to Avoid Avoid contact with water and chemicals. The mineral is sensitive to high temperatures, which can lead to the loss of water from its structure and damage to the specimen. Prolonged exposure to intense light, especially sunlight, can cause fading or darkening of the color. As an arsenate, it is toxic – avoid inhaling dust and wash hands after any contact with the mineral. ## Storage Parasymplesite specimens are best stored in closed, darkened boxes or display cases to protect them from light, dust, and mechanical damage. Due to its fragility, avoid placing it in areas prone to vibrations or shocks.