Rare Urchin Quartz

Rare Urchin Quartz
Rare Urchin Quartz (Quartz crystal with Mannardite phontom inside) from Brazil
Photo: Mike Bowers


Star Hollandite Quartz is a type of quartz crystal that has very small inclusions of Hollandite in it, that look like tiny black stars. 

Hollandite is an oxide mineral. A monoclinic-prismatic white mineral containing aluminum, barium, iron, lead, manganese, oxygen, silicon, and sodium. It is the barium-manganese (III) endmember of the coronadite group. 
 
Quartz is a hard, crystalline mineral composed of silica. The atoms are linked in a continuous framework of SiO₄ silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO₂.

Rare quartz inclusion

Hollandite Quartz is a variety of Quartz, silicon dioxide, which has dark grey/black six-pointed “star” inclusions of the mineral Hollandite. Star Hollandite formations are formed when deposits of Hollandite become trapped within Quartz during its formation. As the Hollandite becomes subjected to high thermal temperatures within the Earth, the Hollandite bursts into star formations within the Quartz. This variety of quartz is very rare.

Quartz is a hard, crystalline mineral composed of silicon and oxygen atoms. Quartz belongs to the trigonal crystal system. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end.  Common colored varieties include citrine, rose quartz, amethyst, smoky quartz, milky quartz, and others. These color differentiations arise from the presence of impurities which change the molecular orbitals, causing some electronic transitions to take place in the visible spectrum causing colors.

Hollandite

Hollandite (chemical formula: Ba(Mn4+6Mn3+2)O16 )) is an oxide mineral. It is the barium-manganese (III) endmember of the coronadite group.

Formula: Ba(Mn4+6Mn3+2)O16
Colour: Silvery-grey to greyish black, black
Lustre: Metallic
Hardness: 4 - 6
Specific Gravity: 4.95
Crystal System: Monoclinic
Named in honor of Sir Thomas Henry Holland (22 November 1868, Helston, Cornwall, England – 15 May 1947, Surbiton, London), geologist and educational administrator.


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