Fluorite in the St. Lawrence veins is mostly massive and coarsely crystalline, filling veins from wall to wall. Close to the vein walls, the fluorite is commonly finely banded. In the larger veins, fluorite surrounds sharp fragments of granite. The most common gangue mineral is quartz, occurring in the material locally known as “blastonite”, which is brecciated fluorite cemented by a mixture of microcrystalline quartz and fluorite, as mentioned above. Nodular forms of fluorite and calcite are common in larger veins mainly along the footwalls (Williamson, 1956). Calcite occurs in nearly all the fluorite veins. Barite, galena, sphalerite, and hematite are common, while chalcopyrite, pyrite, bornite, covellite, and chalcocite are less common (Harris, 1995a). Sulphides (mainly galena and sphalerite) are more common near the contacts of the veins, or where the vein cuts into the country rocks. It is possible that sulphide content of the veins may increase in the deeper parts of the veins (Van Alstine, 1948).

The fluorspar veins at St. Lawrence are complex structures along fault zones within the St. Lawrence granite and related porphyries. Commonly, the faults exhibit evidence for multiple episodes of movement. Typically, the veins have a high-grade core, and irregular amounts of mineralized brecciated granitic material along one or both walls. Three major types of fluorite veins are recognized, as follows:

• Low-grade veins, with an average width of 5 m to 7 ........

The current plan is to develop two underground mines at St. Lawrence, Tarefare and Blue Beach North. The average dilution for both mines is 18% (17% at TF and 20% at BBN) which RPA considers reasonable for the selected mining method. RPA concludes that:

• The Alimak method would provide the best stoping alternative, taking into consideration development requirements, ground support requirements and overall economics, compared to the sublevel longhole method.

• As BBN and TF will be mined in series, some mobile equipment will be transferred between sites, and some production development at TF will be completed by owner crews rather than contractor crews.

- subscription is required.