Leucaugite

Character
Under leucaugite are included generally light-colored pyroxenes that contain aluminum with little or no iron or manganese. The variety as here described is ill-defined, as there are no analyses of such pyroxenes from Franklin, and their assignment has depended wholly on qualitative chemical tests.

Occurrence
At Franklin large pyroxene crystals of the prismatic habit shown in figure 80 were found in abundance in a pocket in limestone between the two legs of the ore deposit, not far from Double Rock, a formerly existing prominent outcrop of pegmatite near the Trotter mine.

Figure 80
Crystal of leucaugite showing the forms b(010), a(100), m(110), p(101), u(111), and s(111). Franklin.

This pyroxene is best represented by two very large matrix specimens in the Kemble collection, the larger one being 18 inches square. The stout prismatic crystals, which have been carefully excavated from the enclosing calcite, are grayish white and commonly reach a length of 2 to 3 inches. They are associated with dark-brown garnet in dodecahedral crystals.

Groups of similar appearance were found at the Gooseberry mine on Balls Hill, associated with scapolite and black garnet. Crystals of this habit, illustrated by figure 81, are best represented in the Canfield collection now in the United States National Museum.

Figure 81
Crystal of leucaugite showing the forms c(001), b(010), a(100), m(110) and s(111). Balls Hill, Franklin.

At Sterling Hill gray to pale greenish-white, opaque crystals, sharply formed and of large dimensions, reach a length of 10-½ inches. The habit-long to short prismatic—is shown in figures 82, 83, and 84.

Figure 82 Crystal of leucaugite showing the forms c(001), b(010), a(100), m(110). Sterling Hill.
	Figure 83 Projection on the clinopinacoid of a crystal of leucaugite twinned on the orthopinacoid, showing the forms c(001), b(010), a(100), m(110), s(111) and o(221). Sterling Hill.
Figure 84 Crystal of leucaugite showing the c(001), b(010), a(100), m(110), e(011), p(101), u(111), s(111), and o(221). Sterling Hill.

Such crystals were seen in the Canfield collection in great variety of form and habit, and one is shown in plate 8, B. They were found in a single large pocket in limestone, associated only with edenite of peculiar habit, during the construction of a tram road near the mouth of the tunnel that gave access to the Noble mine. They are remarkable for their perfection of form associated with large size and complex habit.

A crystal in the Canfield collection, from another locality of pyroxene crystals of peculiar habit, placed in this variety doubtfully in the absence of chemical tests, is shown in figure 85.

Figure 85
Crystal of pyroxene showing the forms b(010), a(100), m(110), y(101), G(201) and R(132). Sterling Hill.

The medium-sized crystals are blackish and are peculiar in their domatic terminations. They come from the ore body at Sterling Hill, probably from the locality that yielded abundant roepperite.


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