Image: <bdi><a href="https://www.wikidata.org/wiki/Q56247090" class="extiw" title="d:Q56247090"><span title="mineral collector and dealer">Robert M. Lavinsky</span></a></bdi> (CC BY-SA 3.0)
orthorhombicuncommonSulfides
Marcasite
FeS₂
This specimen displays a cluster of radiating, spear-shaped orthorhombic marcasite crystals, exhibiting a pale brassy-yellow metallic luster, characteristic of its coxcomb or cockscomb habit.
Marcasite Physical Properties
Mohs Hardness
6Crystal System
orthorhombicLuster
metallicStreak Color
greenish-black to brownish-blackCleavage
poor/indistinctFracture
uneven to conchoidalSpecific Gravity
4.89Colors
pale bronze-yellow, brass-yellow, tarnished iridescentTransparency
opaqueType Locality
Panasqueira, Covilhã, Castelo Branco District, PortugalMineral Group
SulfidesUses
jewelry (historically), sulfur ore, collectorAssociated Minerals
pyrite, galena, sphalerite, calcite, quartzRarity
uncommonGeological Context
Marcasite forms in low-temperature, acidic environments, often found in sedimentary rocks, coal seams, and hydrothermal veins. It is a polymorph of pyrite, but less stable and prone to decomposition.
