Atsuo Okamoto, Corn Exchange, Edinburgh<br/>Iran do Espirito Santo, Ingleby Gallery, Edinburgh<br/>Impressionist Gardens, National Galleries of Scotland, Edinburgh

Meet Atsuo Okamoto, who stitches together slabs of rock into seemingly weightless marvels

Japanese sculptor Atsuo Okamoto moves mountains – literally.

The artist crafts gargantuan, natural blocks of stone found in the quarries of Ibaragi, central Japan, into strikingly hewn granite pillars, 12 of which stand like a mini Stonehenge in the Corn Exchange Gallery. Nothing is as sobering as the stark sight of a dozen man-sized stone pieces lined up in three rows of four (Faraway Mountain, 2006). But don't be put off by the leaden description. The columns don't impose on their environment, they nestle into the air. This chunk of rock is unassuming.

Okamoto makes the sculpture mass manageable through his use of a traditional Japanese carving technique known as wari modoshi ("splitting and returning") whereby he cuts a block into 12 slabs with a diminutive "mame ya" or "bean" wedge. Next, the columns are dismantled further into hand-held morsels. These portions are then stitched meticulously back together: you can see the joins in the granite works, the shallow notches, the roughly hewn and smoother segments fused in a patchwork. It's arresting, intelligent stuff, a world away from, say, the heavy bulks of Henry Moore.

Two smaller, tea-cosy-shaped sculptures (Turtle Project: Volume of Lives) jar, however. Okamoto retrieved more than 50 stone pieces sent to various individuals worldwide between 2002 and 2008, piecing together the personal relics to reunite the original whole stone, a laborious project not to my liking. A pair of his sculptures also grace the Gayfield Square Gardens down the road; these vulnerable human figures (Forest H-1/Forest H-2, 2008), kneeling and standing, are pitted from head to foot with light-filled indentations that make the solid forms seem weightless.

If Okamoto has a lightness of touch, then the art of Sao Paulo-based Iran do Espirito Santo is positively gossamer. This conceptually rigorous, minimalist art looks radically different with every viewing. A hand-painted, four-part wall piece made up of gradations from white through to black (En Passant 5, 2010), takes on a fresh perspective in the changing light of day, triggering spatial and temporal nuances.

But that's not the most seductive work on show. It's a shame you can't touch the art, because the sculptures, from the illusionistic, bewitching crystal creation Water Glass 2 (2008) to a sinister, enlarged stainless steel shaft (Silver Pencil, 2010), cry out to be handled and explored. How does he achieve such unsullied, flawless forms? Where does the bottomless crystal vessel begin and end? When did Minimalism become so delicious and enticing? We want to fully embrace the contours of his work; it's more physical than visual. Note also the tonal mutations in the "Standby" photogram series (2010). Such touches make Iran do Espirito Santo an essential stop on the Edinburgh circuit.

There could not be greater contrast between the clean, crisp lines of Iran's art and Impressionist Gardens. Walking through the first room, decorated with works by Impressionist precursors such as the unsung French painter Paul Huet, made me wonder how much lightly mottled foliage a man could take (incredibly, this is the first ever exhibition devoted to the subject). But there are numerous uplifting crowd-pleasers here, from three lily-pond paintings included in Monet's Waterscapes exhibition of 1909, to exceptional pieces by Pierre Bonnard, Camille Pissarro and Gustave Caillebotte. The selection, arranged in four accessible sections, demonstrates a blooming new impetus in turn-of-the-century art, eschewing the mythological subjects and religious themes of the Old Masters.

Comprehensive as the show is, the curators have tried to touch one base too many; a work by Italian Divisionist Gaetano Previati (Mammina, 1908), for instance, seems superfluous. It may well follow in the Impressionist tradition of portraying children, but the canvas, with its strident, linear strokes, looks out of place against Impressionism's flickering palette.

But a convincing case is made, through works by Turin artist Marco Calderini and Henri Le Sidaner, for thematic and technical links between Impressionism and counterpart movement Symbolism. Those mad about Monet (and magnolias) should grab the well-written, accomplished catalogue.

Atsuo Okamoto (0131-561 7300 ), to 30 Sep; Iran do Espirito Santo (0131-556 4441), 25 Sep; 'Impressionist Gardens' (0131-624 6560), to 17 Oct

Next Week:

Ossian Ward falls in with the Romantics at Tate Britain