Barkstone castor was the prefered castor of the day during the day when they used castor in the perfume trade. it was considered the cadilac of castor. very large, very hard, and very aromatic. yellowish in color if i remember right. That particular castor is formed thru genetics, some say dating back to prehistoric days. thats why you only see it once in awhile. j you can bet that those females you caught in the same water system are related to the beaver of last year. You will prolly see it again in that same watershed. Thorpe "does" use it when he can find it or buy it but it doesnt come along very often.