Hyalite Opal on Schorl and Feldspar - NER 077 

Measurements:  58 x 33 x 33 mm 

Description:  Prolific aggregates of hyalite opal sit on a conglomorate matrix of shorl and feldspar. Some of the schorl crystals have the 'Mercedes sign' terminations.

It fluoresces beautifully under ultraviolet light. One photograph was taken in natural daylight.

The specimen has a few nicks and contact marks.

Chemical Composition:  SiO2•1.5(H2O)  (opal)
                                       NaFe²⁺₃Al₆Si₆O₁₈(BO₃)₃(OH)₄  (schorl)                                                KAlSi₃O₈  (feldspar) 

Hardness on Mohs Scale:  (opal)  5.5-6 
                                         (schorl )  7.5                                                                                       (feldspar)  6 - 6.5               

Location:  Erongo, Namibia.

Specimen Code:  NER 077