This rock is from the Jakobsberg mine, Filipstad, Värmland, Sweden, and consists of a fine grained, olive/tan colored matrix with calcite inclusions and a visible white encrustation of margarosanite. As seen in the photograph below, taken under short wave UV, the margarosanite fluoresces bright blue and the calcite red. Other than Franklin, New Jersey, the Värmland area of Sweden is the only other known source for margarosanite.
Bright blue fluorescent margarosanite and red fluorescent calcite are seen under short wave UV (254nm) on this colorful specimen from the Jakobsberg mine in Sweden. The size of this piece is 80 x 43 x 16 mm.
Same specimen seen under visible light. The margarosanite is a surface coating on a fine grained, olive/tan colored matrix with calcite inclusions.