Found as Cosmic Anomaly in 0.5. Valuable asteroids. My Mackinaw full of Ytrium is over 60 mil.

It contains multiple ore:

• Ytrium, 0.6m3 (240 Iso) - Many rocks, two dozen, the field is mostly these. 1-20km3
• Jet Ochre, 8m3 (1564 Mex, 1380 Iso, 368 Nox) - One rock, about 12,000m3
• Pellucid Crokite (920 Pye, 2300 Mex, 920 Nox) - One rock, about 17,000m3
• Eifyrium (266 Zydrine) - One rock, about 33,000m3
• Ducinium (170 Megacyte) - One rock, about 22,000m3

It appears Ytrium is the best source of Isogen.