Danielsite

Chemical formula: (Cu,Ag)<sub>14</sub>HgS<sub>8</sub>

Danielsite is a very rare copper, silver, and mercury sulfide, forming tiny, metallic grains in association with other sulfides.

## Characteristics Danielsite is a mineral from the sulfide group, which is visually difficult to distinguish from other similar minerals without advanced analysis. It occurs as very small, anhedral (lacking characteristic crystal faces) grains, not exceeding 150 micrometers in size. These grains are typically intergrown with other minerals, most often with galena. Due to its size and opacity, most visual characteristics are observed under a microscope in reflected light. ## Physical Properties Danielsite is characterized by a metallic luster and is an opaque mineral. Its hardness and density have not been precisely measured due to its small size and rarity. In reflected light, its color is described as grayish-white, with a slight creamy tint compared to the surrounding galena. ## Colors and Varieties This mineral does not exhibit color variation and does not form varieties. Its uniform, grayish-white color is a constant feature observed under the microscope. ## History and Name Danielsite was first described in 1986 by W.G. Mumme and A.I. Tsortis. The mineral is named in honor of Dr. John L. Daniels, an Australian geologist who discovered the deposit from which the first samples of this mineral originated. The type locality (locus typicus) is the Coppin Pool prospect in the Chichester Range, Western Australia. ## Uses Due to its extreme rarity and microscopic size, danielsenite has no commercial or industrial applications. It is solely an object of scientific interest and for specialized micromineral collectors.

Properties

Luster
Metallic
Streak
Black
Cleavage
None
Fracture
Uneven
Transparency
Opaque
Crystal system
Isometric

Diagnostic features

## Identification Identification of danielsenite is possible only through advanced laboratory techniques, such as reflected light microscopy, chemical composition analysis using an electron microprobe (EDS/WDS), and X-ray diffraction (XRD). It is impossible to identify with the naked eye in field conditions or in a collection. ## Distinguishing from Similar Minerals Under the microscope, danielsenite can be confused with many other sulfides of similar gray color in reflected light, such as acanthite, argentite, or other complex sulfosalts. Chemical analysis, which will show the simultaneous presence of copper, silver, and mercury in appropriate proportions, is crucial for differentiation. ## Crystal Forms Danielsit occurs exclusively as anhedral, irregular grains that are intergrown with other minerals, mainly galena. It has not been observed in the form of well-developed crystals.

Geological environment

## Genesis Danielsit is a mineral of hydrothermal origin. It forms in the final stages of crystallization in ore veins, under conditions enriched in copper, silver, and mercury. In its type locality, it is associated with mineralization processes within volcanic rocks. ## Mineral Associations This mineral most often co-occurs with galena, in which it forms inclusions. Other associated minerals in the type locality include chalcocite, covellite, pyrite, sphalerite, and other rarer sulfides and sulfosalts. ## Localities The only confirmed and described locality of danielsenite in the world is its type locality – the Coppin Pool prospect, Chichester Range, in the Pilbara region of Western Australia.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a danielsenite specimen is assessed solely based on scientific, not aesthetic, criteria. The most valuable samples are those where the presence of the mineral has been confirmed by analysis, and the grains are large enough (on a micro scale) to be studied. The specimen must come from a confirmed locality and be well-documented. ## Popular Localities The only source of danielsenite specimens is its type locality in Western Australia. The mineral is not available on the commercial collector's market and is found only in the collections of scientific institutions and a few highly specialized micromineral collectors.

Care and storage

## Cleaning Specimens containing danielsenite, typically microminerals in polished sections or intergrown in a rock matrix, generally do not require cleaning. If absolutely necessary, compressed air can be used to remove dust. Any contact with water and chemicals should be avoided. ## What to Avoid Avoid all chemicals, acids, and even water, which could react with the mineral or associated minerals (e.g., sulfides). The mineral may be susceptible to oxidation. It should be protected from moisture and atmospheric contaminants. ## Storage Specimens containing danielsenite should be stored under stable, dry conditions. The best solution is a sealed "micromount" box, which protects the sample from dust, moisture, and mechanical damage.

External references

Sources

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