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Where is Ruby in Zoisite found?

Ruby in Zoisite

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Ruby in Zoisite occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.

Where to find Ruby in Zoisite

Tanzania (Longido district)

The primary and most famous source of high-quality Ruby in Zoisite (Anyolite). Discovered in 1956, these deposits are known for large, well-formed ruby crystals within a vibrant green zoisite matrix.

Kenya

Similar geological settings to Tanzania, producing comparable material.

India

Some occurrences of ruby in zoisite have been reported, though generally not as prolific or as high quality as the Tanzanian material.

Norway

Minor occurrences of zoisite with corundum have been noted, but not typically marketed as 'Ruby in Zoisite' in the same way as the African material.

Collecting tips

  1. Geological Context. Look for areas with known occurrences of metamorphosed mafic or ultramafic rocks, especially those associated with regional metamorphic belts.
  2. Color Identification. The distinctive green, red, and black coloration is a key identifier. The green zoisite is often granular, and the red ruby will stand out against it.
  3. Hardness Test. Ruby (9 on Mohs) is significantly harder than zoisite (6-7 on Mohs). This difference can be observed by attempting to scratch the green zoisite with a ruby crystal (if exposed) or by noting the differential wear in polished specimens.
  4. Specific Gravity. The rock will feel relatively dense due to the presence of ruby (SG 3.9-4.1) and zoisite (SG 3.15-3.38).

Quick Check

Color:
Green (zoisite), Red (ruby), Black (hornblende)
Luster:
Vitreous to pearly (zoisite), Adamantine to vitreous (ruby)
Streak:
White (for zoisite and ruby, though typically not performed on a rock assemblage)

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