The remains include a square-shaped 16ft-tall structure which had been buried under 65ft of sand.
Hawass said: "There was so much sand dumped here that no one had any idea there was something buried underneath."
Hawass' team has been excavating at the location for two years. Just two months ago they determined the structure, with sides about 72ft long, was the base of a pyramid.
They also found parts of the pyramid's white limestone casing - believed to have once covered the structure - which enabled them to calculate that the complete pyramid was once 45ft high.
The pyramid is the 118th discovered in Egypt.
Hawass said he believes the pyramid belonged to Queen Sesheshet, who is thought to have played a significant role in establishing the 6th dynasty and in uniting two branches of the feuding royal family.
Her son, Teti, is thought to have ruled for about 20 years until he was assassinated, a sign of the time's turbulence.