Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
In this section we will explore some of the classic tools developed by Dr. W. William Hanneman as described in his Guide to Affordable Gemology, with some updated observations made by me, Barbra Voltaire. , which I think may be helpful to all.
This section is an open, round table discussion. Therefore, anyone wishing to add tips, questions or confusions, is welcome to jump right in to this thread!
I am going to start with the instrument I start every stone identification (except diamonds) using.
The Polariscope. Definition: A polariscope uses polarized light for gem identification. It can be easily constructed by attaching 2 properly oriented squares of plastic polarizing material to a support rod. Proper orientation is crossing the filters at right angles so that NO light can penetrate them. When you look through both filters it will appear dark. This is known as the “crossed position”. In order to use this for gemological purposes, The crossed polars must be back lit. This can be done with something as simple as placing them on a night light, or setting them in front of a mag light. Here is the setup used by Dr. Hanneman: Simply attach the polarized sheets to a support and backlight:
Barbra’s Tip. Nowadays most all of us carry a cell phone or tablet or have easy access to a laptop. All these screens are polarized. Therefore, they can act as one of your filters and the light source, in a pinch. Your reaction between the screen and a polarized sheet will be paler than using 2 polarized sheets but it is definitely detectable. With 2 polarized sheets you can just use the phone or pad as a light source. Voila! Polariscope in the pocket. Here is a set-up on my ipad:
My only note would be that many phone screens are circularly polarized now (probably to avoid interacting with plane polarized sunglasses). My current and previous phones both have this "feature."
Post subject: Re: Dr. Hanneman's Tips: 1:Polariscope
Posted: Mon Oct 26, 2015 9:37 pm
Gemology Online Veteran
Joined: Sun Oct 29, 2006 11:43 pm Posts: 514 Location: North Carolina
Bought 2 - 49mm Polarizing Linear PL Lens Filter - for $7.98 total on ebay. 2 inch PVC pipe and a nightlight plus some cutting of the pipe makes a desk polariscope.
Post subject: Re: Dr. Hanneman's Tips: 1:Polariscope
Posted: Mon Oct 26, 2015 10:20 pm
Site Admin
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Pictures, Bob? Sounds like a winner. _______________________ FYI 49mm= approx 2" _______________________
I was thinking since I have 3" square polarized sheets, I could cut them down slightly to 2" and use the leftover for a Hanneman dichroscope! I'll follow up with 2: Dichroscope.
____________________________________________________________________________________ FYI2: One polarizing filter makes the screen on my MacBook Pro go totally black. _____________________________________________________________________________________
Post subject: Re: Dr. Hanneman's Tips: 1:Polariscope
Posted: Tue Oct 27, 2015 2:00 am
Gemology Online Veteran
Joined: Sat May 22, 2010 2:51 am Posts: 755 Location: South Africa
Barbra Voltaire wrote:
I need some tips on mocking up a coniscope. Anyone?
A 10x loupe inserted between the stone and the upper polarizer produces conoscopic images of the interference figure. The photograph shows a more elaborate set-up, but the principle is illustrated.
Attachments:
Polariscope.jpg [ 148.17 KiB | Viewed 2493 times ]
Last edited by Duncan Miller on Sat Oct 31, 2015 2:04 am, edited 1 time in total.
Post subject: Re: Dr. Hanneman's Tips: 1:Polariscope
Posted: Sat Dec 05, 2015 11:53 pm
Gold Member
Joined: Mon May 26, 2014 9:42 pm Posts: 1033
Hi - I just made a polariscope from a piece of PVC pipe, a bit of plexiglass two polarized filters a couple rounds of wood, and a dollar store light. Cut PVC into three sections. cut wood rounds to fit on top of them. Drill holes in wood rounds. Glue wood rounds on top of two pieces of PVC pipe. Glue polaroid filter over holes. Glue one round piece of plexiglass that fits inside the pipe on top of one polaroid filter. Glue one round piece of pexiglass on top of the third piece of pvc.
Glue two of the PVC pieces together. One that has the glass on top, on top of the one that has the filter NOT covered with glass.
Glass glue PVC glue filter wood glue PVC
glass glue filter PVC
Light is turned on and the thing assembled. Rotate the top piece until the polarizers are crossed.
Users browsing this forum: No registered users and 19 guests
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot post attachments in this forum