A beautiful Pyrrhotite Sphalerite Cluster also featuring small quartz crystals, on matrix. The Pyrrhotite crystals are medium sized. Looks like an interesting Sphalerite Crystal in the crevice of the matrix. This is a great piece to show the different shapes of the two minerals, which are often found together. A very nice piece from a collectible location. Pyrrhotite crystals are rare and hard to come by. Mounted on a perspex pad for enhanced display.
Dalnegorsk, Russian Federation.
6.9cm x 6.2cm x 3.5cm, 152g.
Named in 1847 by Ours Pierre Armand Petit Dufrenoy from Greek “pyrrhos”, flame-coloured. Pyrrhotite has some unusual characteristics. First, it has an unusual formula. The amount of sulfur does vary by roughly 20% or 50 to 55 atoms of sulfur per 50 atoms of iron. Or is it the iron that varies? Really the same difference. Thus the unusual formula of Fe1-xS. Secondly, it has two symmetries. While this should indicate that there are two minerals and not one, in the case of pyrrhotite, mineralogists have made an exception. When pyrrhotite is low in sulfur and the formula is closer to true FeS, then the structure is hexagonal. But when it is high in sulfur, the structure is monoclinic. Clearly two different symmetries, two different formulae; therefore, two different minerals except, in natural pyrrhotite crystals both phases are present in the same crystal. If you are a purist, you can think of a pyrrhotite crystal as an assemblage of two minerals, but most minerologists treat it as one.
Thirdly, pyrrhotite is magnetic or at least weakly so. It is the next most common magnetic mineral to magnetite. Although not all specimens will show great evidence of magnetism if any, some will attract a paperclip or needle suspended from a string or move the needle of a compass. Massive pyrrhotite is common and magnetism is sometimes the only way to distinguish it from other brassy colored sulfides such as chalcopyrite, pyrite, pentlandite or marcasite. Good crystals are rare and should rightly be treasured as coming from a very unusual mineral.
Sphalerite, also known as Blende or Zinc Blende, is the major ore of zinc. When pure (with little or no iron) it forms clear crystals with colours ranging from pale yellow (known as Cleiophane) to orange and red shades (known as Ruby Blende), but as iron content increases it forms dark, opaque metallic crystals (known as Marmatite).
Quartz is the most common mineral found on the surface of the Earth. A significant component of many igneous, metamorphic and sedimentary rocks, this natural form of silicon dioxide is found in an impressive range of varieties and colours. There are many names for different varieties.