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Basanite


#1

Richard, the question of basanite came up the other day and I tried
to find a good definition of it in our books (of which we have very
many) and couldn’t. Can you tell me what you think/know it is?

Thanks

Jan
Jan MacLellan
Mountain Gems Ltd.
4611 Hastings Street, Burnaby, BC Canada


#2

According to the book, Gemstones of the World, Sterling Publishing,
basanite is a “black, fine-grained jasper from North Carolina used by
jewelers and goldsmiths for streak tests of precious metals”.
According to the Dictionary of Gems and Gemology by Robert M. Shipley,
published by the GIA, it is a " Lydian stone, or touchstone. Velvety
black quartz used for testing the color of the streak of metals".

Joel Schwalb
@schwalbstudio
http://www.schwalbstudio.com


#3

Jan, just in case you didn’t get the definition of Basanite, here it
is: bas�a�nite Pronunciation: (bas’u-nIt", baz’-), [key] �n. Petrog. a
basaltic rock composed chiefly of plagioclase, olivine, and augite.

Richard


#4

Basanite is a popular name for a fine grained black Basalt. It is
sometimes used for backing Opal doublets and triplets. The thermal
expansion rate is supposed to be very similar to that of Opal, thus
putting less strain on the glue joints of these assembled stones when
subjected to temperature changes. Hope this helps.

Michael Howe, GG
Trigon Holding Co.
http://www.trigonholding.com


#5

Jan, I have lots of books as well, and have failed at finding that
particular word. I suspect it’s a geological/mineralogical term
derived from “basalt” because basanite is a very fine-grained, dense
form of basalt that takes a great polish. I used to collect my own on
field trips in Idaho and Oregon but don’t know anyone who sells it
commercially these days. The term was used widely in the Pacific
Northwest when I lived there and in the 1970s and 80s and it was sold
by rough stone dealers. For a definition I’d suggest looking in
geology or mineralogy texts. Maybe the new edition of Pough’s Field
Guide? Mine dates to the 1950s…time for me to email Amazon. Most
of my other books are gemology-specific. But I’m sure some Orchidian
out there has the final answer.

Rick Martin


#6

Yes, I have always heard Basanite referred to as a very dense basalt
that would take a good polish. Rose Alene McArthur @O_B_McArthurs


#7

Basanite is a name used for two different materials. It comes from
the Greek basanos, touchstone. The sedimentary variety is a black
siliceous shale (similar to jasper). The igneous variety is a very
fine grained basaltic rock similar to tephrite. Will E.