Church exterior The church is traditional in form, consisting of a tall gable-roofed nave, a crossing and intersecting transepts, with a hipped polygonal apse at the western end. The nave is flanked by a pair of skillion-roofed aisles, which, being at a considerably lower level, allow for clerestory windows to the upper portion of the nave. In the north-eastern corner, the incomplete stump of the tower forms a dominant vertical element. A number of smaller-proposed semi-detached single-storey elements project from the main bulk of the church: two pairs of chapels flanking the apse, the cluster of hip-roofed sacristies in the south-western corner, and the former
baptistery in the south-eastern corner. The church itself is of brick construction, with an external stone facing. It has a plinth of rock-faced Malmesbury bluestone, which is surmounted by a course of splayed blocks of Mount Somers limestone. Above this is the facing of Barrabool Hills sandstone. Two types of limestone, both of
New Zealand origin, have been used for the external dressings: Mount Somers limestone for the plinth course, doorjambs and window tracery, and
Oamaru limestone for all other dressings. The colonettes, flanking the window and door openings, are of polished Aberdeen (red) granite. The roof of the church is clad in Westmorland
slate, with 'tile ridging'. Westmorland slate is of English origin; it has a tendency to be green in colour, in contrast to the blue-coloured slate from Wales. The slates are doubled-nailed with copper nails. The original 'tile ridging' was replaced in 1941. At the crossing of the roof is a flêche, substantially of pressed zinc on timber framing. This is in the form of a polygonal shaft with eight trefoil-arched openings, containing louvred vents, surmounted by a tapering conical spire, clad partly with rounded slate, and partly with flat sheet zinc. The flêche is further embellished with a row of projecting decorative elements at the base of the spire, and a Latin cross, once gilded, at the apex. The Fitzgerald Tower, as it was named in the 1890s, remains incomplete. It was originally to be 162 feet (about fifty metres) tall, to the tip of the spire. The tower, presently consisting of the equivalent of only two storeys, is square in plan, with intersecting buttresses at each corner. The first floor level (approximately in line with the roof of the aisle) is articulated by a course of splayed limestone blocks, and the upper level by an arcaded limestone frieze, consisting of a row of trefoil arches supported on squat columns with cushion capitals.
Church interior Main portion of the church The church is planned on the traditional Latin cross form. The total interior length, from east to west, is long, or, as described in a contemporary source: 'nearly three chains, or three times the width of Bourke Street'. The church is wide, from transept to transept, or 'being five feet narrower than Elizabeth Street, from shop window to shop window'. The bulk of the east–west portion of the church is wide, and comprises a
nave, flanked by two aisles and three pairs of projecting alcoves, three of which are used as confessionals. At the east end of the nave is the organ gallery, accessed via a staircase in the northeast corner. In the corresponding south-eastern corner is the original baptistery, now used as a Chapel of
Saint Josemaría. The main portion of the church is divided into five bays, with arcades separating the nave and the flanking aisles. Each arcade is supported on six Jork Swedish red granite columns, worked and polished in Scotland. These columns are arranged so as not to intercept the view of the
high altar from the aisles. The columns have capitals of foliated form artistically treated so as to appear alike, but the detail of each differs materially. The columns have marble bases, which, in turn, are supported on smoothly rutted Malmsbury bluestone plinths. The columns each bear a polished brass plate at the base of the shaft, inscribed with the name of the parishioner or the parish organization who funded the cost of that column.
Sanctuary and chapels St Mary's contains four side chapels in addition to the main altar. The sanctuary is flanked by a pair of chapels, dedicated to the
Sacred Heart (south) and the
Blessed Virgin Mary (north). Flanking these large chapels are two smaller chapels, which front the transepts, dedicated to Saints of Ireland (south) and
Saint Joseph (north). All four chapels and the sanctuary, terminate in semi-octagonal forms. The sanctuary and chapels are separated from the nave and transept by a white marble altar rail, installed in 1927, which is pierced by repetitive quatrefoils. The sanctuary and each of the chapels are accessed via separate openings with ornate brass gates. The canted walls of the sanctuary and chapels have clusters of columns and half columns at their intersections. Some marble inlay is of Pyrenean (Spanish) rose marble; other columns are scagliola. Scagliola, which dates back to the 17th century or earlier, is a form of plastering which imitates marble, or other fine stone. Scagliola columns are traditionally made by forming a substrate of thin strips of metal or wood which are lathed and covered with a coating of lime and hair. The columns are then coated with a mix of gypsum plaster and glue, tinted accordingly. The dense and highly polished finish is achieved by rubbing with pumice, charcoal, linen cloth and, finally, felt impregnated with oil. The floor of the sanctuary and side chapels is covered with a marble mosaic pavement installed in 1927. The mosaic tiling comprises off-white tiles, set into a square grid of yellow tiles, with an ornate geometric and foliated border of black, grey and yellow tiles. The design incorporates a number of circular panels, including symbolic representations of a Pascal lamb (representing Christ), a sailing ship (representing the Star of the Sea), a Latin cross, a basket with loaves and fish (representing the Eucharist), and the monograms of the Sacred Heart and the Blessed Virgin Mary.
Organ The colony's leading organ builder,
George Fincham, worked on St Mary's organ from 1898 to 1900. It was the first pipe organ in Australia to be classified by the National Trust and is well regarded as an instrument of national importance. It is Australia's largest 19th-century organ still intact. The majority of Fincham's larger organs have been greatly altered or destroyed. The only two substantial examples of his later work which survive largely intact are the instruments at St Joseph's Parish in
Warrnambool (1892) and at St Mary's, restored in 1993. While building St Mary's organ, in September 1899, Fincham suffered a paralytic stroke, from which he fully recovered. He admitted his son Leslie as a partner in the firm in 1900 which was henceforth known as George Fincham & Son. Fincham Sr continued to be actively involved as an organ builder until his death on 21 December 1910. ==Film==