In version 1.15 the automatic hammerer won't process the following:

• Astral Silver Ore Gravel
• Atlarus Ore Gravel
• Carmot Ore Gravel
• Orchalcum Ore Gravel
• Oureclase Gravel Ore

Small addition. Silver, lead, tin and aluminium ore also don't work in the hammerer. gold, iron, osmium and copper ore are hammered in the machine, thereby producing broken ores.

Just as an update on this:
This can be fixed by moving to the Ex Nihilo Ore Creation System (and also fixes #5). I'll be moving to this, but it will break existing dusts in the world.

• Meutoite Ore Gravel

• Infuscolium Ore Gravel

• Rubracium Ore Gravel

• Deep Iron Ore Gravel

• Adamantine Ore Gravel

• Prometheum Ore Gravel

• Mithril Ore Gravel

  They also don't get processed

It also doesn't process Cobalt and Ardite gravel. It does process the sand versions.

This is actually a bigger issue than I first thought when I looked into it. All Ex Astris registered ores are not going through the auto hammer currently.

Just to let you know as of version 1.16.26, there are 4 gravel ores that still do not work with the auto hammer.

Alduorite Ore Gravel
Ceruclase Ore Gravel
Kalenrite Ore Gravel
Vulcanite Ore Gravel

Edit:
I've found a few others that aren't working as well:

Vyroxeres Ore Gravel
Lenurite Ore Gravel
Midasium Ore Gravel
Sanguinite Ore Gravel
Shadow Iron Ore Gravel

I will note that these ores are all nether versions. Could be an issue with the nether ores mod. Or at least the nether ore from metallugy.

all others, gravel and sand versions, seem to be working though.

I actually think this has been impacted in the latest versions. Note though that dusts are still going into the Auto Hammerer.

I just updated both ex nihilo and ex astris and can confirm that this has been fixed