Omumbiri, the name used by the Himba of Namibia, is a resin from the Commiphora wildii, a species of myrrh tree. It has a lemony scent that actually reminds me more of Omani frankincense than myrrh.
It's hard to tell from this picture but the colors vary from a creamy bright lemon yellow to a warm burnt amber to a deep red to black. This was stored with ground resin so it looks a bit 'ashy'.
The resin is very dry to the touch and can be crushed easily into a powder. It becomes very light in weight and floats in the air so I suggest wearing a mask when grinding this up. I used the ground powder to tincture.
Omumbiri oil is also available from Aftelier (under the name Myrrh from Namibia). I diluted the oil to 10% and compared it to the tincture. What I found was the tincture had a cool, fresh and mild lemon-pepper scent while the diluted oil was warmer and more resinous, earthy. On a scent strip the tincture faded quickly while the dilution lasted hours even becoming a bit stronger over time. I can see both having a place in perfume blends depending on what I'm looking to achieve. The resin can be purchased from African Aromatics.