1. LapDigest News for Issue No. 40
The next Digest will be published on Thursday or Friday of this week, as we have to go out of town for a day or so.
If you have queries about hardness of materials or density or specific gravity, please send them in now. We will start running the paper on hardness when we resume.
.. and wear safety glasses and a mask when needed; let's make lapidary safe AND fun!
We have found Sun Stone in Oregon, which is a form of feldspar and also have seen it come from Madagascar (Species not remembered). You didn't give a description, so that would be helpful, but both forms are natural. The Oregon Sun Stone is untreated, but not sure about the Madagascar material.
Sun stone is a microcline, aventurescent labradorite, or oligoclase feldspar. Hardness: 6 to 6.5 Found in several states but best material I have seen came from Oregon. Subject to cleavage, use care when setting.
Subject: RE: What is "Sunstone"
CORDIERITE - SUNSTONE OF THE VIKINGS?
The mineral cordierite is thought to be the source of the famous sunstone of the Vikings, who in the ninth century were expert navigators. Without benefit of compass, Viking sailors managed to ply their watery routes of conquest and commerce, navigating by the stars at night and the sun during the day. No matter what the weather, according to ancient Scandinavian sagas, the sun could be located with the aid of the magical "Sun Stone." Summarizing sunstone lore in a recent article in the archaeology magazine Skalk, Danish archaeologist Thorkild Ramskau lamented that none of the sagas clearly describe the sun stone. "But there seems to be a possibility," he wrote, "that it was aninstrument which in cloudy weather would showwhere the sun was." Now, with a clue supplied by a young archaeology enthusiast, Ramskau has discovered the secret of the sun-seeking stone of the ancients.
To the 10-year-old son of Jorgen Jensen, chief navigator of the Scandinavian
Airline System, the instrument described in Skalk sounded like the twilight
compass used by his father at higher latitudes, where the magnetic compass
is unreliable. The twilight compass is equipped with a polarizing filter
that enables a navigator to locate the sun-- even when it is behind the
clouds or below the horizon--by the light polarized by the atmosphere.
Intrigued by his son's observation, Jensen passed it on to Ramskau, who
immediately recognized its scientific implications. Enlisting the aid
of Denmark's Royal Court jeweler, the archaeologist collected minerals
found in Scandinavia whose molecules are aligned parallel to each other
just as the crystals are in a polarizing filter. Ramskau found that one
of these minerals, a transparent crystal called cordierite, turned gray
to violet-blue whenever its natural molecular alignment was held at right
angles to the plane of polarized light f!
Putting cordierite to the test, Ramskau accompanied navigator Jensen on a flight to Greenland, keeping track of the sun with his stone while Jensen used the twilight compass. His observations were accurate within 2.5 degrees of the sun's true position, and he was able to track the sun until it dipped 7 degrees below the horizon.
"I now feel convinced," Ramskau concludes, "that the old Vikings, with the aid of their sun stones, could navigate with enormous accuracy."
[Why not polish your variously hard slabs separately first, then cut them out and build the intarsia polished-side-down on a dead-flat surface like a piece of plate glass? If you support the glass on blocks, you can peek underneath to see how it looks. When the piece is complete, you can apply mortar and reinforcement to the back to get a slab of concrete with the intarsia adhered to one side.]
Andrew Werby - United Artworks
(BTW-I too experience the 'scroll sideways' problem. DX2-50 running Netscape Nav. under 3.1)
Each author is requested to write the words "-- non-commercial republish