gypsum is softer than barytes.
"Geology"
James Geikie
Huge flagons, coated with gypsum, were brought in shoulder high, each with a label attesting that it was the great Falernian vintage of Opimius, one hundred years old.
"Roman Society from Nero to Marcus Aurelius"
Samuel Dill
If it be green tea, prepared by large infusion of Prussian blue and gypsum, or black tea mixed with pulverized black lead, you may expect there will be a poisonous effect in the conversation and the moral health damaged.
"Around The Tea-Table"
T. De Witt Talmage