The phrase "although it was unknown" is correct and usable in written English.
You can use it to introduce a contrast or exception regarding something that is not known or recognized.
Example: "The origins of the artifact were intriguing, although it was unknown to the researchers at the time."
Alternatives: "even though it was not known" or "despite being unknown".
The request was not honored, although it was unknown whether Mr. Williams was aware of it.
In the United States, the Food and Drug Administration reported on Friday that Pfizer Inc. had said that six patients taking the drug had died, although it was unknown if Viagra played any role in the deaths.
In our newly prepared drug delivery system, the adsorption of acetylcholine on SWCNT was confirmed by Raman spectrum, although it was unknown whether acetylcholine was adsorbed on the surfaces or in the tubes of SWCNT.
Early on October 6 while the hurricane was moving through the Bahamas, a ship reported a pressure of 958 mbar, although it was unknown if it was in the center or the periphery of the storm.
Although it was unknown whether all 73 QTLs identified for domestication-related traits had independent gene actions on each trait, the observed number of QTLs was compared with the expected number of QTLs based on each LG length (Table 7).
That means less than 0.5% of Facebook's active mobile users have installed Home – although it's unknown what percentage of its user base own Android devices.
Ferguson's office said that at least nine people were detained as a result of the practice, although it is unknown how many were deported.
The Glittering-bellied Emerald is one of the most broadly distributed of southern South American hummingbirds, although it is unknown from Chile.
Although it is unknown exactly how many will clear that bar, it is certain that the contingent from Russia will be depleted significantly.
Although it's unknown whether stress levels in medical training are worse today, more and more young physicians have chosen to share family responsibilities.
Although it's unknown how much longer the improvement in fluid intelligence will last, Jaeggi doubts the effects will be permanent without continued practice.
