... not sure what to tell you.
You may need to port your own or wait for others to get around to it.
I tried a quick search in the Open Solaris Forums, drivers sub-forum.
Keyword INTEL found one solitary vague reference to the ixge NIC instance.
search =http://www.opensolaris.org/jive/search.jspa?objID=f79&q=intel
vague reference, Mar '05 = http://www.opensolaris.org/jive/thread.jspa?messageID=38022#38022
A Google search on keyword 'ixge' was not very helpful.
http://www.google.com/search?hl=en&q=ixge&btnG=Google+Search
The Solaris HCL suggests the driver is native to the 6/06 release of Solaris 10.
http://www.sun.com/bigadmin/hcl/data/sol/components/details/1535.html
However that's the Multi-mode fiber card, not UTP copper.
Intel's web site references Windows, Linux and FreeBSD, as of Jul '05 for that MMF card,
http://www.intel.com/network/connectivity/products/pro10GbE_SR_server_adapter.h tm
and only Linux and FreeBSD for the UTP card, as of Oct '05 (Notice ... not for Windows ! )
http://www.intel.com/network/connectivity/products/pro10GbE_CX4_server_adapter. htm