Browsing Archive: August, 2020

PLAYING WITH QUARTZ SPHERES IN POLARISED LIGHT

Posted by Site Moderator Webmaster on Monday, August 24, 2020, In : Lapidary 
Duncan Miller

It’s play time!  For this exercise you need a flat computer screen with an open blank Word page, a smallish clear quartz crystal, a quartz sphere if you have one, or if not, some clear quartz beads (glass beads won't work), plus a pair of cinema 3D glasses or Polaroid sunglasses. 

Quartz crystals are anisotropic. This means that a ray of light travelling through the crystal is split into two polarised rays, vibrating at right angles to each other. There is only one directio...


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Stories Behind Some Recently Acquired ‘Exotic’ Rocks and Polished Spheres

Posted by Site Moderator Webmaster on Sunday, August 23, 2020, In : Mineralogy 

by Peter Rosewarne

With the lockdown in force it’s given me some time to revisit my passion for igneous rocks and their minerals, being what we used to call a ‘min and pet’ man whilst studying geology at Kingston University back in the early 70s. Of particular interest to me on the local scene are the Bushveld Igneous Complex, the Pilanesburg Alkaline Complex, kimberlites, ultramafics and the Vredefort Dome.  In my quest to find specimens of the ‘type’ rocks from these sites, in a...


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