I am a stone beadmaker with 40 years experience and those , if they are stone , look exactly like chert. Chert is a type of jasper but of sedimentary not igneous origin. In the American Pacific north-west we have lots of very similar chert of oceanic origin , radiolarian chert. We seldom cut it because it all has very small blebs of random rocks in it just as your beads have. In the modern bead world the blebs keep the beads from selling despite the range of pleasant blues and greens of the chert.

There is nothing not to love about these, the material is as tough as it gets, I have been accumulating them for a number of years, some of my favorites. They are as hard, dense and as heavy as any Jasper. Found primarily in Mali and Mauritania

Our friend David Ebbinghouse wearing a strand I sourced for him over the years.....this material is often found with Amazonite but it's much denser and tougher

the stone is absolutely not sedimentary, it is not porous and the fractures are concoidal as in chalcedony

The " porcelain " jaspers of the American west such as Biggs and Bruneau are other examples of sedimentary jaspers , chert. They are very dense and are much harder of an absolute ( not mohs n) scale than crystalline quartz. The oceanic sedimentary jaspers form from the vast amount of silica falling from dead micro organisms in the ocean water column.They get metamorphosed when the oceanic plate is subducted and get back to the surface when parts of the plate they are in are obducted.The western US jaspers are freshwater deposits of silica leached from basalt then concentrated in voids in the basalt. Oceanic cherts are extremely common in the geology of California , Washington and BC.They take many forms due to various contaminants and how much they were disturbed while forming. Green , blue , black , red and silver cherts are common in the mountains near me in Washington and are often found in blocks hundreds of yards across.Sedimentary rocks are not all porous in fact most " sedimentary "rocks have a sedimentary stage then are cooked either in subduction zones or by regional metamorphism. Hardness has nothing to do with porosity as very hard Brazilian agate is famous for it's porosity , porosity which allowed it to be the basis of the dyed bead trade of Idar.

http://www.quartzpage.de/flint.html

It is all well and fine to discuss NW American sources of jasper. But let's remember that the beads being discussed are from NW Africa.

All quartz has essentially the same hardness. There is not 'softer' nor 'harder' quartz (whether massively crystalline or microcrystalline). What makes jasper different is the structure of the microcrystals. These are interwoven in such a way that the material is more-tough than other varieties. This is one important reason that, in antiquity (in India) chert was used for making drill-bits for making beads. But they have the same hardness.

Regarding the "dying" of chalcedony, here is one of many dialogues I posted on this topic. I hope this clarifies why it is important to not say "dyed stone" when this is not factually correct:

http://beadcollector.net/cgi-bin/anyboard.cgi?fvp=/openforum/&cmd=iYz&aK=51301&iZz=51301&gV=0&kQz=&aO=1&iWz=0

gzi, gZi, GZI

dzi, dZi, DZI

zi, Zi, ZI

But not "Dzi."

P.S. I have a zi bead shirt too—but it's a different one that I received from Walt Seifried. J.

an older link from 2009 discussing these beads

.....and Joyce, I don't know the story on David's dZi shirt, you'll be able to catch up with him in January