I've noticed that some icebreaker clothing is labeled as "black sheep" merino wool and the same with other brands, so I am wondering if someone can explain or link to something that explains well what the differences are.
Using the Way back machine for http://www.icebreaker.com/en/black_sheep (which used to exist, but search engines still link to) it said:
The ultimate in luxury, soft merino wool clothing, the Icebreaker Black Sheep collection is made from the finest fibers to create a beautifully soft and lightweight line. Comfortable enough to wear day or night, our long-sleeved tops and sweaters are perfect for every activity – whether at the office or sitting by the campfire. Because the Icebreaker Black Sheep line is crafted from our softest and finest merino fibers it is ideal for the modern traveler due to its low bulk and ability to fold small. The perfect night time camping wear, this comfortable clothing collection can be layered over some of our simple base layers or worn on its own. The beautifully soft merino wool finds the perfect balance between ultimate style and luxurious comfort.
So it appears that the "blacksheep" merino wool is softer and lighter than regular merino wool. I'm not sure if it has anything to do with actual black sheep though.
There are two possible explanations that I can think of,
The wool comes from rare actual black merino sheep.
Do you have natural colored Merino sheep?
Yes, we do. Black Merino sheep are quite rare and it took us many years to build up our flock to a sizeable number.
This is marketing by people who know that humans want to stand out in a crowd by being different and buying expensive/rare things, hence the black sheep label.
See this advertisement that calls it Merion Black Sheep wool but doesn't say that it comes from black sheep.
There's a reason most of us wear denim 90% of the time—it looks good, feels comfortable, and is tough as nails. But when it comes to hiking and climbing, denim is definitely lacking, well, at least it was. Ortovox is changing the denim game with its Women's Merino Black Sheep Denim Pants, which were designed with climbers in mind and are composed of a cotton, merino wool, and elastane blend for bomber durability, awesome stretch, and killer comfort. The addition of a Cordura stretch inseam gusset adds to their overall durability and mobility while smart features like a brush pocket, zippered map pocket, and chalk bag loop make them a solid choice for an evening at the climbing gym or a day at the crag.
Personally, I would bet on explanation 2 as I kind of doubt that it actually comes from black sheep.