The sixth is the "hyalite," which has but a glassy or vitreous lustre, and is found almost exclusively in the form of globules, or clusters of globules, somewhat after the form and size of bunches of grapes; hence the name "botryoidal" is often applied to this variety.
"The Chemistry, Properties and Tests of Precious Stones"
John Mastin
These shells occur at Hartlepool and Sunderland, where the rock assumes an oolitic and botryoidal character.
"The Student's Elements of Geology"
Sir Charles Lyell