Men's fashion question---Silk t-shirts?

My company just sent out an amended reminder on the workplace dress code. Among other things, it says that silk t-shirts with sport jackets are acceptable in the “business casual” context. I may be one of the people squeaking by in black jeans during the week, but I can’t imagine how a silk t-shirt would be acceptable. Can anyone provide a link to a picture of the sort of garment they’re talking about? What is the “look”?

here

Argg, isn’t that a female mannikin/shirt? I would like to get this right, since it will now be the only kind of shortsleeved shirt that I can fold into my gym bag in the morning.