A bad day for junk bonds is helping push Blackstone to new post-IPO lows – but another issue is starting to surface: how are analysts going to value the private equity giant.

Sell-side analysts gearing up to launch coverage on Blackstone, which went public last month, will face a host of challenges including limited access and few publicly-traded comparable companies.

To make private equity — and arguably hedge funds — work, youve got to keep it confidential, said Brad Hintz, a Sanford Bernstein analyst who follows brokers and investment banks. And if you keep it confidential, the analyst has a very difficult time valuing it.”

“Unfortunately that often leads to one of two extremes: massive over-valuation with the assumption that you own the goose that lays the golden egg. Or massive under-valuation because its a big black box and you have no faith in your ability to forecast anything.

With dust settling after its IPO, Blackstone may be finding investors less sanguine about holding the rich but cryptically valued units. Perhaps anticipating difficulty communicating with analysts, last month the embattled private equity firm hired Joan Solotar as senior managing director overseeing public markets.

Solotar who will manage relationships with analysts formerly directed equity research at BofA and was herself a top-ranked analyst.