LAZULITE: TUCSON GEM SHOW: MAIN SHOW

In attending the Tucson “main show” I remained on a hunt for the best $5 mineral I could find at the venue.  Now, there are very few $5 minerals for sale in the Convention Center but there are numerous five figure minerals a buyer could take home!  But, the hunt is the fun part of the chase and I brought home some nice crystals of lazulite a magnesium, iron, aluminum phosphate [(Mg,Fe⁺⁺)Al₂(PO₄)₂(OH)₂].  Lazulite is often a sky-blue to azure-blue color but my crystals are such a very deep blue or blackish-blue that the camera will not pick up such---as is the case for crystals collected at the well-known Rapid Creek locality in the Yukon, Canada. Crystals from Rapid Creek are stubby bipyramids, have a vitreous luster and are transparent to translucent.  On the Rapid Creek crystals a strong light will transmit through the specimens and produce the beautiful blue color.  Crystals are fairly hard at 5.5-6.0 (Mohs).

 

Bi-pyramidal crystals of deep blue to black-blue lazulite (L) and quartz (Q) collected from Rapid Creek, Yukon Territory, Canada. Width of specimen ~1.75 cm.

Luzulite is found in high grade metamorphic rocks where it is associated with kyanite, corundum, andalusite and others.  It also may be found in some massive hydrothermal pegmatites. The magnesium-rich lazulite is in a solid solution series with the iron end member scorzalite [(Fe⁺⁺,Mg)Al₂(OH,PO₄)₂].

Two photomicrographs picking up the dark blue color of lazulite crystals, each has a maximum width of ~ 3 mm.  Also present are tiny terminated quartz crystals.

It is easy to confuse lazulite with lazurite, a blue variety of the mineral Hauyne, a sodium-calcium tectosilicate with sulfur, sulfate and chloride.  Lazurite is found associated with pyrite in zones of contact metamorphism of limestone and is the major “blue” component of lapis lazuli (a mixture of lazurite, pyrite, calcite). 

In my hunt for the best $5 mineral at the different show venues, I sought advice from a friendly Arizona rattlesnake:

·       Be flexible

·       Keep a low profile

·       Think before you strike

·       Soak up some sun

·       Shed your old ways

·       Be thick skinned

·       Don’t get rattled