These specimens from the Siglo XX Mine present defined, brilliant, translucent and light orange colour monazite-(Ce) crystals. They are accompanied by hyaline quartz and black-brown cassiterite on matrix. Some are twinned. Monazite is found in small quantities in this mine.
Monazite gets its name from the Greek word μουάζω "monazein" meaning "to be alone," alluding to its isolated crystals and their rarity when they were first found. Monazite is generally found in granitic pegmatites, but these crystals are found in hydrothermal veins with tin and the absence of thorium (generally an accompanying element of monazite).

Size: 7.7 x 5.5 x 4.9 cm.
Main crystal: 3.5 mm.

Col J. Viñals. Col. E. Nicolau (Barcelona).

This is a really good crystal cluster of bismuthinite from the Mina Tazna in Bolivia. It is formed by large, terminated, prismatic crystals of bismuthinite, divergent, gray metallic. Some crystals show a metallic patina from a thin coating of marcasite/pyrite. On the back side some quartz crystals and gray-white uncovered metallic natural bismuthinite crystals. The Tazna Mine is a historic bismuth-tungsten mine in the high Andes of Bolivia that has produced noteworthy specimens for decades. Samples with this quality are very rare seen on the market. Specially for connoisseur "gray" mineral collectors...

Size: 5.8 x 4 x 3.8 cm.
Main crystal: 19 mm.
Found in ±1980.

Col. J. Viñals, Col. E. Nicolau.
Classic locality

In this Bolivian Andean mining area, around 2010-2013, a small area with antimony and silver ore was found, highlighting some specimens of stephanite, a silver sulfoantimonide. This floater specimen is formed by a group of interpenetrated crystals, with parallel growth, and showing orthorhombic prism shapes with striations and complex terminal faces. It is distinguished from pyrargyrite by being completely opaque to light, while the latter usually gives red colors (red silvers). An exceptional specimen reminiscent of the best and ancient Mexican stephanite, although this is from the Porco mine, the oldest and most significant silver mine in Bolivia.

Size: 2.2 x 1.4 x 1.1 cm.
Found in 2010-2013.

In this Bolivian Andean mining area, around 2010-2013, a small area with antimony and silver ore was found, highlighting some specimens of stephanite, a silver sulfoantimonide. This floater specimen is formed by a group of interpenetrated crystals, with parallel growth, and showing orthorhombic prism shapes with striations and complex terminal faces, some of them are doubly terminated. It is distinguished from pyrargyrite by being completely opaque to light, while the latter usually gives red colors (red silvers). An exceptional specimen reminiscent of the best and ancient Mexican stephanite, although this is from the Porco mine, the oldest and most significant silver mine in Bolivia.

Size: 1.7 x 1.5 x 1.1 cm.
Found in 2010-2013.

In this Bolivian Andean mining area, around 2010-2013, a small area with antimony and silver ore was found, highlighting some specimens of stephanite, a silver sulfoantimonide. This floater specimen is formed by a group of interpenetrated crystals, with parallel growth, and showing orthorhombic prism shapes with striations and complex terminal faces. It is distinguished from pyrargyrite by being completely opaque to light, while the latter usually gives red colors (red silvers). An exceptional specimen reminiscent of the best and ancient Mexican stephanite, although this is from the Porco mine, the oldest and most significant silver mine in Bolivia.

Size: 2 x 1.7 x 1.4 cm.
Found in 2010-2013.

In this Bolivian Andean mining area, around 2010-2013, a small area with antimony and silver ore was found, highlighting some specimens of stephanite, a silver sulfoantimonide. This floater specimen is formed by a group of interpenetrated crystals, with parallel growth, and showing orthorhombic prism shapes with striations and complex terminal faces, some of them are doubly terminated. It is distinguished from pyrargyrite by being completely opaque to light, while the latter usually gives red colors (red silvers). An exceptional specimen reminiscent of the best and ancient Mexican stephanite, although this is from the Porco mine, the oldest and most significant silver mine in Bolivia.

Size: 2.1 x 1.5 x 1.3 cm.
Found in 2010-2013.

In this specimen we can observe a large group of augelite crystals, very brilliant, transparent and with very well defined faces and edges. Under magnification we can see that these crystals are richly faceted and have a pseudorhomboidal shape. They are accompanied on the matrix by small white prismatic crystals of baryte, along with numerous octahedral pyrite crystals. This specimen belongs from the Laskowski collection and is accompanied by various labels.

Size: 6.7 x 5.7 x 2.6 cm.
Main crystal: 5 mm.

Col. Erich Laskowski.

Specimens of magnetite from Cerro Huañaquino were well known decades ago, but today it is not easy to find them, and even less with the quality of this specimen that we propose. It is a druse of very bright octahedral crystals with an intense black colour that are disposed on the rocky matrix.

Size: 8.9 x 5 x 3.5 cm.
Main crystal: 7 mm.

Specimens of magnetite from Cerro Huañaquino were well known decades ago, but today it is not easy to find them, and even less with the quality of this specimen that we propose. It is a druse of very bright octahedral crystals with an intense black colour that are disposed on the rocky matrix.

 

Size: 7.8 x 6.8 x 2.8 cm.
Main crystal: 1.5 cm.

Specimen of a little-known locality. These sample shows aggregates of silver crystals, with an intense luster and tones between white and golden. They are disposed on a matrix with quartz and iron oxides with which they contrast.

Size: 6.4 x 4.8 x 2 cm.
Main crystal: 8 mm.
Found in 08/2011

The Siglo XX mine is one of the most impressive Bolivian mining localities. It produces some amazing specimens of common species like quartz, few of the with the Japan-Law twin which are are well known in the mineral world. In this sample we can enjoy a good sized Japan-twin quartz crystals, with transparence and luster. This nice twin is disposed on a druse of hyaline quartz crystals.
To give a unique touch to the specimen a group of cassiterite crystals with good brilliance and deep black color, very rich in faces, interpenetrating between them and with some quartz crystals. A superb specimen.

Size: 11.0 x 6.8 x 6.3 cm.
Main crystal: 25 x 15 mm. (macla/twin)

Rich group of octahedral magnetite crystals with a good size. Brilliant, intense gray metallic tone and disposed very aesthetically on the rocky matrix. A classic that is hard to see on the market.

Size: 12.0 x 10.4 x 4.5 cm.
Main crystal: 13 x 12 mm.
Found in 2002.

Ex-col. Joan Rosell.
Magnetic properties: It is attracted by magnets

Perfection! A nice crystal of vivianite, with a deep green color and well defined. With transparence that show the green tone characteristic for the species. Very aerial disposed on a solid sandstone matrix, sulfur free which ensures the stability of the specimen in the future. It is better in live than on the photo, but enjoy them. An exceptional specimen.

Size: 6,9 x 6,5 x 4,5 cm.
Main crystal: 38 x 20 mm.

Precio reducido-Reduced price 310€

Group of Sigloite crystals pseudomorph after Paravauxite, partially covering the rocky matrix. Paravauxite and sigloite differ chemically by the presence of a single water molecule. Sigloite is white to yellowish. The Siglo XX Mine is the type locality for Sigloite species.

Size: 5.5 x 3.5 x 2.5 cm
Main crystal: 9 x 2 mm

Fluorescent under long wave UV