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Rock Art => Cabochons, Intarsias, Cameos => Topic started by: christos on November 14, 2023, 08:37:31 PM

Title: Black Onyx?
Post by: christos on November 14, 2023, 08:37:31 PM
Hi, How do i go about formulating an cutting approach?
Title: Re: Black Onyx?
Post by: R.U. Sirius on November 15, 2023, 07:58:14 AM
It's nice the way it is. Cutting and grinding it will make you realize just how much softer the white vein is (calcite?) than the black parts of it (basalt?). You can already see differential weathering if you look at the dips in the outline.
 
Title: Re: Black Onyx?
Post by: lithicbeads on November 15, 2023, 04:46:05 PM
I do ones like this quite often and just make a long tapered bead , or a few , with black on either side and the white streak at an angle just off the middle of the length of the stone. Around here on the beach they are typically hornfels  that have been intruded by quartz.
Title: Re: Black Onyx?
Post by: christos on November 17, 2023, 11:54:51 AM
It's nice the way it is. Cutting and grinding it will make you realize just how much softer the white vein is (calcite?) than the black parts of it (basalt?). You can already see differential weathering if you look at the dips in the outline.
Yes it is softer and in this lime mineral are mini crystals of quartz  1/2 mm. it could be basalt it coul be a silicate usualy basalt nodules are not shinny as much and the area has obsidian also. i found a shoreside cliff with a layer of obsidian about 5 meters from top so its dangerous but ..
Title: Re: Black Onyx?
Post by: christos on November 17, 2023, 11:57:01 AM
I do ones like this quite often and just make a long tapered bead , or a few , with black on either side and the white streak at an angle just off the middle of the length of the stone. Around here on the beach they are typically hornfels  that have been intruded by quartz.
do you mean oval round  or beads?
Title: Re: Black Onyx?
Post by: christos on November 18, 2023, 09:22:03 PM
top and bot view of beach rock on a beach with numerous such rocks. im confused but understand its a risk anyway i start cutting it.( first pic is side which can be barely seen in 2 new photos. )
Title: Re: Black Onyx?
Post by: lithicbeads on November 19, 2023, 08:45:01 AM
 Obsidian on the beach ? Extremely unlikely.
Title: Re: Black Onyx?
Post by: christos on November 19, 2023, 12:12:16 PM
Obsidian on the beach ? Extremely unlikely.
I heard that about meteorites also...