Forums Cutting Material and Identification How dark is TOO dark?

  • How dark is TOO dark?

    Posted by pierreleroux on April 7, 2016 at 6:25 am

    Dear members,
    In my local rivers, we find really nice garnets, density around 3.85-4.15, colour fro raspberry thourgh purple, with the odd orange, but mostly deep red ( not really brownish red)

    My question: How do I determine if a gem is too dark to cut a good faceted stone? and b) what designs work well?

    If I understand the “white paper test”, I should be able to see a pool of colour on a piece of white paper placed under the gem, in bright sunlight – can another, more standardized light source be substituted?

    Designs for cutting dark material seems to have as many opinions as there are cutters? I have started off with the concept that “less is more” in the pavilion facets, but lately seem to think that a good brilliant cut works well in the material I have here (I am attaching a few pics, if I can figure out how) Comments please

    pierreleroux replied 7 years, 3 months ago 3 Members · 4 Replies
  • 4 Replies
  • Alan Balmer

    Administrator
    April 7, 2016 at 2:51 pm

    Here’s a good writeup on the white paper test, by John Bailey.
    http://facetingacademy.com/learn-facetinWhitePaper

    I’m attempting to contact a long-neglected friend who I remember as something of an expert on dark garnet. If I get information, I’ll post it here, with his permission.

  • Alan Balmer

    Administrator
    April 7, 2016 at 5:31 pm

    Matt Dunkle has cut a number of dark Namanga garnets. His suggestions are:

    Use anything from 37.5° to 39° with a shallow crown (I seem to remember using 35° a lot). Also, if you can find it, use a 7 main SRB cut – anything that affords larger facets. Hex designs should work well, as long as they are not too complicated (less than 60 facets). You want broad flashes that return large volumes of light.

  • erniehawes

    Member
    April 28, 2016 at 5:31 pm

    Your pictures appear to be typical of red garnets. How big are the stones pictured? Where are the rivers located that you are finding these garnets?

  • pierreleroux

    Member
    April 19, 2017 at 1:04 pm

    Hi Ernie, sorry about the long delay in answering: The stones in my pictures range fro 5 carats ( finished weight) to 11 carats – so were about 3-4x that size before I started on them. I’ve learnt to drop the pavilion angles to around 39 degrees, which still gives good light return, but does reduce the light appreciably

    The stones are found in the Linthipe River, one of the main rivers that originates near Lilongwe in Malawi, and there are a main source of alluvial garnets near the town of Salima on the Lake, near my hometown of Chipoka. Colours range fro deep orange through reds to purple, and some do show some colour change from sunlight to fluorescent, but I havn’t gotten round to doing a proper screening yet

Log in to reply.