The context of this is I'm replenishing stocks for jumponium after using ~50 premium boosts traversing to the Outer Arm Vacuus [Explorers Bar & Grill].
Firstly how not to find Arsenic - I tried many Geological Signals on several different high As % worlds and didn't get any from a Geo signal. I believe there are already known statistical reasons in the way these finds are generated that pretty much preclude stuff like As from appearing at them in any of the Crystalline features. You'll get much rarer stuff but not As.
So surface prospecting.
I picked a HMC (32.6% metal) with 2.1% As and vowed not to leave until I'd found myself 10 pieces i.e. 30 units. In all it took me about 12 hrs of prospecting, zooming around on a pretty flat world.
Metallic Meterorites: around a 1:30 chance of finding a single piece of As.
Bronzite Chondrite: Absolute no chance. I found plenty of these and not a single one gave As.
Mesosiderite: 1:10
Outcrop: 1:10
I quickly maxed out in all the other "rarer" raw mats from there such as Cadmium, Tin and Ruthenium.
Of course this was only one world: Eowyg Aihm JW-E d11-1 B-3
www.edsm.net
I hope this helps!
Firstly how not to find Arsenic - I tried many Geological Signals on several different high As % worlds and didn't get any from a Geo signal. I believe there are already known statistical reasons in the way these finds are generated that pretty much preclude stuff like As from appearing at them in any of the Crystalline features. You'll get much rarer stuff but not As.
So surface prospecting.
I picked a HMC (32.6% metal) with 2.1% As and vowed not to leave until I'd found myself 10 pieces i.e. 30 units. In all it took me about 12 hrs of prospecting, zooming around on a pretty flat world.
Metallic Meterorites: around a 1:30 chance of finding a single piece of As.
Bronzite Chondrite: Absolute no chance. I found plenty of these and not a single one gave As.
Mesosiderite: 1:10
Outcrop: 1:10
I quickly maxed out in all the other "rarer" raw mats from there such as Cadmium, Tin and Ruthenium.
Of course this was only one world: Eowyg Aihm JW-E d11-1 B-3

EDSM - Elite Dangerous Star Map
The Galactic Positioning System of Elite: Dangerous at your service.

I hope this helps!