• Chemistry: Pb9Sb8S21, Lead Antimony Sulfide.
  • Class: Sulfides
  • Subclass: Sulfosalts
  • Group: Fuloppite
  • Uses: As mineral specimens and as a very minor ore of lead.
  • Specimens

Semseyite forms interesting aggregates of intergrown tabular crystals that are rather unique. The mineral is named for an Hungarian mineral collector, A. Semsy. Semseyite is another rare sulfosalt, a segment of sulfides where the antimony acts more like a metal than a non-metal and occupies a position where it is bonded to sulfurs. Semseyite is also one of several lead antimony sulfides, an informal group of similar minerals. Some of these minerals belong to the formal group of minerals known as the Fuloppite Group. These minerals are rather similar in characteristics and are difficult to distinguish from one another. Other members of the Fuloppite Group include fuloppite, plagionite, heteromorphite and rayite.


  • Color is gray to black.
  • Luster is metallic.
  • Transparency: Crystals are opaque.
  • Crystal System: Monoclinic; 2/m.
  • Crystal Habits include radial to spherical aggregates of tabular nearly parallel crystals.
  • Cleavage is perfect in several oblique directions.
  • Hardness is 2.5
  • Specific Gravity is 5.8 - 6.1 (heavier than average for metallic minerals)
  • Streak is black.
  • Associated Minerals include quartz, pyrite, stibnite and several other rare sulfosalts.
  • Notable Occurrences are limited to the type locality of Baia Sprie, Maramures, Romania as well as the Glendinning Antimony Mine, Glenshanna Burn, Dumfrieshire, Scotland; France and Turkey
  • Best Field Indicators are crystal habit, associations, density and cleavage.
SEMSEYITE specimens:
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SEMSEYITE specimen sem-1
$ 57.00
Dims:1.7x0.7x0.7" (4.3x1.8x1.8 cm)
Wt: 1.0oz. (27g)
Mine des Anglais, Cantal, France
This specimen consists of a piece of massive lead-gray semseyite with a bit of drusy quartz. Near the quartz are a couple of very tiny cavities. It appears that there may be crystals of semseyite within these tiny vugs, but I cannot be certain. The cavities are just too tiny.
no photo
sem-1 ($ 57.00)
Mine des Anglais, Cantal, France
SEMSEYITE specimen sem-2
$ 90.00
Dims:2.5x1.4x0.6" (6.4x3.6x1.5 cm)
Wt: 3.4oz. (97g)
Herja, Kisbanya, Romania
A frust of semseyite crystals covers a massive pyrite matrix in this specimen. These crystals are prismatic and striated. They reach 0.3" (0.8cm) in length. There is also a small amount of quartz crystals on this specimen. The only damage visible is on the edges, where it was pried from the host rock.
no photo
sem-2 ($ 90.00)
Herja, Kisbanya, Romania


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