Simonellite
Chemical formula: C<sub>19</sub>H<sub>24</sub>
Simonellite is a rare, natural hydrocarbon, forming soft, colorless or yellowish crystals in fossil wood and lignite.
Properties
- Mohs hardness
- 1-2
- Luster
- Vitreous to resinous
- Streak
- White
- Density
- 1.05-1.10
- Cleavage
- Perfect on {010}
- Fracture
- Conchoidal
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Key diagnostic features of simonellite include its extreme softness (it can be scratched with a fingernail), very low density, and perfect cleavage in one direction. Its fluorescence is also characteristic – it exhibits a blue glow under ultraviolet light. It melts in a match flame. However, the most important indicator is its specific occurrence environment – lignite and fossil wood. ## Distinguishing from Similar Minerals Simonellite is sometimes confused with another hydrocarbon, fichtelite, with which it often co-occurs. However, fichtelite crystallizes in the monoclinic system and usually forms crystals of a different shape. Other natural resins, such as retinite, are amorphous and do not exhibit cleavage. Gypsum, although sometimes similar in appearance, is distinctly harder (2 on the Mohs scale) and much denser. ## Crystal Forms Simonellite forms thin, tabular crystals with a rhombic or hexagonal outline. These crystals often group into fan-shaped or rosette aggregates, growing on the surface of lignite or in its fractures.
Geological environment
## Genesis Simonellite is a mineral of organic origin. It forms as a result of diagenetic processes (transformations) of terpenoid compounds derived from conifer resins. This process occurs under anaerobic conditions, within buried sediments containing plant matter, mainly in lignites (brown coal) and fossil wood. ## Mineral Associations It most often co-occurs with fichtelite, another rare hydrocarbon. It is also accompanied by minerals typical of sedimentary environments, such as gypsum, native sulfur, and, above all, the parent material – lignite. ## Localities The type locality, from which historical specimens originate, is Fognano, Tuscany, Italy. Other known localities include brown coal mines in Saxony (Germany), some sites in the Czech Republic (e.g., Bílina mine), and isolated occurrences in the United States (California).
Rarity
Rare
For collectors
## Quality Criteria The most valued specimens by collectors are those with well-formed, sharp, and transparent crystals. Rich aggregates in the form of rosettes are also highly regarded, especially when they contrast with the dark color of the matrix (lignite). Crystal size is an important factor, as they are usually small. ## Popular Localities Historical European localities, including the type locality in Tuscany and German brown coal mines, are considered classic and provide the best specimens. Specimens from these locations are sought after due to their historical and scientific significance.
Care and storage
## Cleaning Simonellite specimens should only be dry-cleaned, using a soft brush to remove dust. Due to its softness and reactivity, contact with water and any chemical agents should be avoided. ## What to Avoid The mineral is very sensitive to heat – it melts at approximately 145°C. It should be protected from direct sunlight, prolonged exposure to UV light (which can cause degradation), and contact with organic solvents. It is extremely brittle and soft, so scratches and drops should be avoided. ## Storage It is recommended to store specimens in separate, sealed boxes, at a stable room temperature, away from light and heat sources. It should be isolated from harder minerals to prevent scratching.