Quartz
Two inter-grown XX, up to 4.2cm long; the upper one is covered by a yellowish oxide
4.5x3.2cm
Selvino, Bergamo. Italy
Specimen n.246

Quartz
2 XX in a parallel formation, 1,9cm and 1.1cm long
1.9x1.4cm
Selvino, Bergamo. Italy
Specimen n.914

Quartz
Single X, very transparent. Few and small internal fractures
2.5x1.5cm
Selvino, Bergamo. Italy
Specimen n.251

Quartz
Another perfectly formed, water clear X, 2.5cm long
2.5x1.1cm
Selvino, Bergamo. Italy
Specimen n.912

Quartz
A combination of a main X, 1.9cm, and another oblique X 1.4cm long. Both are very transparent
2.1x0.9cm
Selvino, Bergamo. Italy
Specimen n.913

Quartz
2 very transparent XX, linked together, 2.2cm and 1.3cm long
2.8x1.4cm
Selvino, Bergamo. Italy
Specimen n.915

Quartz
2 XX with a light  yellow coating, 2.7cm and 1.9cm long. The bigger has a clear distortion on a tip
2.9x1.3cm
Selvino, Bergamo. Italy
Specimen n.916

Quartz
An irregular combination of XX, the main one has a tip strongly deformed
4.8x1.8cm
Selvino, Bergamo. Italy
Specimen n.917

Quartz
A small XX, well formed and transparent - 1.1cm long - grown on a bigger one, deformed and with internal factures
2.1x2cm
Selvino, Bergamo. Italy
Specimen n.918

Quartz
Two crossed XX, the bigger is 3.1cm long
3.5x1cm
Selvino, Bergamo. Italy
Specimen n.306

Quartz
A not infrequent formation: a small X, on the top of a bigger one. Inside, there is a negative X, difficult to see without a lens
3.9x1.1cm
Selvino, Bergamo. Italy
Specimen n.534

Quartz
A large biterminated X is surrounded, on both the tips, by two small XX. A nice merge among three pieces. The main X shows inclusions of black hydrocarbons, not visible in this photo
3.5x1.5cm
Selvino, Bergamo. Italy
Specimen n.901

Quartz
Another curiosity from Selvino. It is a combination of 4 XX: the main central, two at the opposite sides. One of them is clearly visible (on he right - 0.9 cm long), the other (on the left) is revealed by the small step in the lower side.  The smaller X is posted centrally, obliquely
3.5x1.2cm
Selvino, Bergamo. Italy
Specimen n.919

Quartz
A merge between two XX, both biterminated, with different dimensions, 0.9 cm large the bigger and 0.5 cm the other
3.5x1cm
Selvino, Bergamo. Italy
Specimen n.902

Quartz
A water-transparent X, with a clear negative X inside
3.1x1.3cm
Selvino, Bergamo. Italy
Specimen n.903

Quartz
Three  biterminated XX, linked together (the bigger is 2.4 cm long), transparent, one of them with a nice clear yellow coating
2.6x2cm
Selvino, Bergamo. Italy
Specimen n.904

Quartz
Cruciform twin, small but perfect
2.1x2.1cm
Selvino, Bergamo. Italy
Specimen n.905

Quartz
A small X (0.8cm long) grown on a surface of a bigger biterminated transparent X 
4x2.6cm
Selvino, Bergamo. Italy
Specimen n.908

Quartz
Single X, very thin (0.7cm), with a lot of internal fractures, on a small amount of matrix
3x1.3cm
Selvino, Bergamo. Italy
Specimen n.906

Quartz
It is not common to find quartz on matrix: in this piece, the X (2.2x1.2cm) stands in a cavity, on the dolomite matrix (it is possible to see small dolomite XX, edge up to 0.4cm), with some coverage of hydrocarbons  
10x6.5cm
Selvino, Bergamo. Italy
Specimen n.244

Another photo: different view

Quartz
A big X (4.8x3.8cm) on a calcite matrix (malformed XX up to 3.5cm). It has a lot of internal fractures and solid inclusions of lime and hydrocarbons, so it is not transparent
10x6.5cm
Selvino, Bergamo. Italy
Specimen n.907

Quartz
Another  piece with matrix. The fat and wide X (2.7x2cm) is  surrounded by calcite malformed and corroded XX, on the dolomite matrix
9x7cm
Selvino, Bergamo. Italy
Specimen n.900