Evenkite

Evenkite
Evenkite from Dubnik, Slovakia
General
Category	Organic mineral
Formula (repeating unit)	C24H50
Strunz classification	10.BA.50
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Space group	Pbcm
Unit cell	a = 7.47, b = 4.98, c = 65.85 [Å]; Z = 4
Identification
Color	Colorless or pale yellow
Crystal habit	Tabular pseudohexagonal crystals, granular, disseminated
Twinning	Polysynthetic
Cleavage	{001} Perfect
Mohs scale hardness	1
Luster	Waxy
Diaphaneity	Transparent
Specific gravity	0.87
Optical properties	Biaxial (+)
Refractive index	nα = 1.504 nβ = 1.504 nγ = 1.553
Birefringence	δ = 0.049
References

Evenkite is a rare hydrocarbon mineral with formula (CH₃)₂(CH₂)₂₂ or C₂₄H₅₀. Chemically it is n-tetracosane.

It was first described in 1953 for the occurrence in the Khavokiperskiye deposit, Lower Tunguska River, Evenkiysky District, Siberia, Russia, where it occurs in vugs within a quartz vein in welded tuff. Associated minerals include quartz, chalcedony, pyrite, pyrrhotite, sphalerite, galena, chalcopyrite and calcite. It was named for the Evenkia district. It has also been reported from the Hautes-Alpes region in France and the Slanské and Vihorlat mountains of Slovakia.

Evenkite C₂₄H₅₀ was first discovered by Shropyshev in the Evenkia district of Siberia, Russia by the Nizhnyaya Tunguska River in quartz geodes. The formation of Evenkite within the quartz geodes where due to thermal cracking of the organic matter (manly marine plants) that where trapped in the septarian concretions during the Jurassic burial. The French Alps region received a lot of geological uplift after the Jurassic burial which increased temperatures that where being applied to the buried sediments. As a result of the high pressure and temperatures, the hydrocarbon is created within the mineral geode. Most commonly found with quartz, evenkite is the last part of the geode to form. In a quartz geode it appears as flaky wax partials on top of the quartz crystals.