This Matrix Shard is trapped in a pocket of ice, and you must use a special item to free it.
Pick up a Hydro-thinner
In the cantina in the base where you first load into the planet, visit the Cantina and purchase a Hydro-thinner from the Vendor behind the bar. The Hydro-thinner item is required for this datacron, and costs 18,000 credits.
This item can not be bought, sold, or traded but it can be put into a guild bank for others to use.
Quicktravel / Taxi / Heroic Shuttle
Republic side, the [HEROIC 2+] Gamorrean Menace heroic shuttle is faster.
Get to the Ice Overhang
Use Hydro-thinner to free the Matrix Shard
Run to the far south of the Highmount Ridge map. While running along the trail, marked as an orange dotted line on the map, you’ll see a glowing white matrix shard trapped in ice, under an icy overhang.
If you have the Hydro-thinner in your inventory, you will be able to go free the Matrix shard just by right-clicking the ice-trapped datacron.