Copiapoa hypogaea barquitensis
(This plant comes in a 3.5" pot. You will receive a very similar plant to the one in the picture. It may or may not be blooming at the time of your purchase. The plant is shipped in its pot to prevent any damage to the roots).
This is a and pretty cool brown cactus. The name 'hypogaea' comes from the Greek for 'underground', referring to the fact that most of the cactus head is usually sunken into the ground. Spines absent or very few short spines.
Recommended temperature zone: 10b-12
Frost tolerance: Avoid any frost 50°F (10°C)
Sun exposure: Part sun. Should be protected from excessive heat and sun
Origin: Coastal Chile (Antofagasta: Chañaral)
Watering needs: Keep fairly dry in winter, water moderately in summer
Blooming habits: Diurnal yellow broad flowers, 0.8" long (2 cm)
Some of the information in this description has been found at desert-tropicals.com, llifle.com and cactus-art.biz