Accessibility options

Switch to preferred accessibility theme:


Increase or decrease the text size:

  • Internet Explorer: View > Text Size > Largest

Keyboard navigation and access keys:

  • A - Accessibility options
  • 0 - Skip navigation
  • 1 - Home
  • 2 - Alexandrite chapters
  • 3 - Alexandrite directory
  • 4 - Alexandrite forums
  • 5 - Alexandrite gemstones
  • 6 - Alexandrite localities
  • 7 - Contact information
  • 8 - About Alexandrite Guide
  • 9 - Sitemap
  • Press ALT + Access Key, then ENTER.

Close

Alexandrite

Tsarstone collectors guide

Brazilian alexandrite

Many finds of low quality alexandrite crystals 2-3 cm in length recorded at Caraiba deposit. Some of the smaller crystals, and sections of larger crystals, are gemstone quality, with excellent clarity and strong color change.

Locality details
CountryBrazil
RegionNortheast Region
ProvinceBahia
LocalityCaraiba mine
Latitude-19.5167
Longitude-43.0333
Altitude3001
Time zoneUTC-3(-2DT)
Locality maps
MapSatellite
Map of Caraiba mine Satellite of Caraiba mine

The Upper Curaca River Valley, characterized by an unremitting flat, low-relief terrain, is situated in a semi-arid tropical ecosystem known as the Caatinga, which has xerophytic vegetation and very shallow residual soils. The Caraiba deposit is a Paleoproterozoic sill-like intrusion consisting of magnetite-bearing hypersthenites, melanorites and norites mainly mineralized with disseminated-type Cu-ore (chalcopyrite and bornite) exploited since 1978.

The intrusion is the largest of a set of 100's mafic-ultramafic bodies found within the Curaca Valley terrain, a N-S trending strip of high-grade rocks in the northern part of the Sao Francisco Craton. This terrain comprises of supracrustais and gneisses of their probable basement, the mafic-ultramafic rocks emplaced as sills, all intruded by G1-G3 early- to late-tectonic tonalitic-granodioritic orthogneisses and granites related to highly ductile deformation events between 2.25 to 2.05 Ga (U-Pb ages of zircons).

The chrysoberyl crystals show a regular pattern of cavities that likely represent inclusions that have weathered away. Others crystals appear to have grown across the foliation of the schist, as shown by trains of micaceous inclusions, which create parting planes and increase susceptibility to physical weathering.


Page 3 of 20 Back to Top << >>
1 2 3 4 5 6 7 8 9 10 ... Last
Bibliographic details
Page title Brazilian alexandrite, Caraiba mine
Author David Weinberg
Website title Alexandrite Tsarstone Collectors Guide
Date published 03 July 2010 06:11 UTC
Date accessed 21 April 2014 11:37 UTC
Permanent link http://www.alexandrite.net/viewpage.html?id=ALXS-001-00004
AMA style
David Weinberg. "Brazilian alexandrite, Caraiba mine". In Alexandrite Tsarstone Collectors Guide. July 03, 2010, 06:11 UTC. Available at: http://www.alexandrite.net/viewpage.html?id=ALXS-001-00004. Accessed April 21, 2014.
APA style
"Brazilian alexandrite, Caraiba mine". (2010, July 03). In Alexandrite Tsarstone Collectors Guide. Retrieved 11:37, April 21, 2014, from http://www.alexandrite.net/viewpage.html?id=ALXS-001-00004.
Bluebook style
"Brazilian alexandrite, Caraiba mine", http://www.alexandrite.net/viewpage.html?id=ALXS-001-00004 (last visited April 21, 2014).
Bluebook: Harvard JOLT style
See Alexandrite Tsarstone Collectors Guide, "Brazilian alexandrite, Caraiba mine", http://www.alexandrite.net/viewpage.html?id=ALXS-001-00004 (Information about Brazilian alexandrite findings and mining in Pindobacu, Brazil.) (as of Apr. 21, 2014, 11:37 GMT).
CBE/CSE style
David Weinberg. "Brazilian alexandrite, Caraiba mine". In Alexandrite Tsarstone Collectors Guide. 2010 Jul 03, 06:11 UTC.[Internet], Alexandrite Tsarstone Collectors Guide; 2010 Jul 03, 06:11 UTC [cited 2014 Apr 21]. Available from: http://www.alexandrite.net/viewpage.html?id=ALXS-001-00004.
Chicago style
David Weinberg, "Brazilian alexandrite, Caraiba mine", http://www.alexandrite.net/viewpage.html?id=ALXS-001-00004, (accessed April 21, 2014).
MLA style
"Brazilian alexandrite, Caraiba mine". Alexandrite Tsarstone Collectors Guide. 03 Jul 2010, 06:11 UTC. 21 Apr 2014 http://www.alexandrite.net/viewpage.html?id=ALXS-001-00004
MHRA style
David Weinberg, "Brazilian alexandrite, Caraiba mine", Alexandrite Tsarstone Collectors Guide, 03 July 2010, 06:11 UTC, http://www.alexandrite.net/viewpage.html?id=ALXS-001-00004 [accessed 21 April 2014].
Close options details