Semseyite with Galena, Sphalerite and Siderite – Herja Mine, Romania

Impressive semseyite specimen from the Herja Mine in Maramureș, Romania. Silvery-grey, sheaf-like to fan-shaped semseyite crystals occur among dark, metallic galena and sphalerite crystals. Numerous light-grey, botryoidal aggregates, possibly spherosiderite, create a striking contrast. An interesting collector’s specimen from one of the classic localities for semseyite.

Semseyite from the Herja Mine, Romania

The Herja Mine near Baia Mare in Maramureș County is one of Romania’s notable historic ore localities. Its hydrothermal deposits are especially known for their diverse sulfide and sulfosalt mineralization. Herja is regarded as a classic locality for well-developed semseyite crystals.

This specimen displays an association of semseyite, galena and sphalerite, together with light-grey aggregates that may consist of siderite. Dark metallic ore minerals cover much of the specimen’s surface, while numerous silvery semseyite crystals stand out between them.

Crystal Habit and Mineral Associations

The most characteristic feature is the sheaf-like and fan-shaped semseyite aggregates. The elongated, tabular to blade-like crystals are partly arranged in radiating groups. They occur predominantly on the front of the specimen, although smaller aggregates can also be identified in several areas on the reverse side.

The galena displays a predominantly stout, complex crystal habit. Alongside approximately cuboctahedral forms, some crystals show irregular, stepped and slightly rounded-looking outlines.

An attractive contrast is provided by numerous light-grey, spherical to botryoidal aggregates, which may represent spherosiderite, a spherical variety of the mineral siderite.

The relationships between the minerals are particularly interesting. Some semseyite aggregates appear to have grown on pre-existing ore crystals. In several places, the light-grey spherical aggregates seem to partially cover the semseyite. This may indicate multiple stages of mineral formation. However, a definitive crystallization sequence cannot be established from macroscopic observations alone.

Measuring 11.5 × 7.5 × 4 cm and weighing 428 g, this is a substantial, richly crystallized specimen from a classic Romanian mining district.