Domain: Natural Science — Geology & Geophysics
Target concept: Crush a marble rock to reveal an irregular, granular fracture surface.

Video generation prompt: On the workbench, a piece of marble about the size of a fist was struck with a hammer and fractured into several pieces; one of the fragments was briefly lifted and turned over.

Evaluation guide:
(i) Target concept: Mechanical fracture of isotropic polycrystalline carbonate rock under localized impact stress.
Minimum mechanism: Marble must be unfoliated, non-cleavable, and composed of equigranular calcite; hammer impact must exceed local tensile strength, causing brittle failure along grain boundaries rather than along planes.
(ii)Storyline: [Frame 1–2] Marble rests statically on workbench surface; hammer enters frame from upper side, approaching marble. [Frame 3–4] Hammer tip contacts marble surface; visible deformation or spark absent (no melting). [Frame 5–6] Fracture initiates at impact site and propagates radially; marble separates into ≥3 distinct fragments with jagged margins. [Frame 7–8] One fragment lifts vertically from workbench, supported by hand/tool; no other fragments move. [Frame 9–10] Lifted fragment rotates fully around horizontal axis until underside faces camera; fracture surface remains fully in focus, evenly lit, and occupies central visual field.

Manual:
Experimental Procedure
1. Place a fist-sized piece of natural marble on a sturdy workbench.
2. Strike the marble firmly once with a geologist's hammer.
3. Immediately select one freshly fractured fragment, lift it from the workbench, and rotate it 180° to expose its underside.
Observation of Experimental Phenomena
The marble fractures into multiple angular pieces; the exposed fracture surface of the turned fragment is irregular (non-planar, non-curved) and granular, made up of many small interlocking calcite crystal grains with no cleavage alignment, giving it a sugary appearance rather than a smooth or flat face.
Summary of Experimental Principles
Marble is a metamorphic rock composed primarily of recrystallized calcite; it lacks planar cleavage and instead exhibits irregular, granular fracture due to isotropic crystal interlocking and absence of dominant foliation or preferred mineral orientation.

Prompt Grounding rubric:
level_1: No marble, no hammer, no workbench, and no fracture/lift action are shown together: e.g., there is no marble at all, no hammer ever appears, or nothing is struck or lifted.
level_2: A marble-like object sits on a bench-like surface, but the hammer never contacts it, or the marble is never actually struck and never fractures, and no fragment is ever lifted.
level_3: The marble sits on the workbench; the hammer strikes it; the marble visibly separates into multiple pieces; at least one fragment is lifted off the workbench, but that fragment is never turned over to show its underside.
level_4: Everything at level 3 holds, and additionally: the lifted fragment is fully turned over so its underside faces the camera, held steadily long enough to be seen clearly, regardless of what that underside actually looks like.
level_5: Everything at level 4 holds, and additionally: the turned-over fragment's underside stays in focus, well lit, and centered in frame (not clipped at the edge, not in shadow, not obstructed by the hand or tool holding it) for a sustained moment, giving a clear, unobstructed view of whatever surface is exposed there.

Scientific and Causal Correctness rubric:
level_1: The marble does not fracture at all after being struck, or it deforms without breaking, crumbles to powder, melts, or shatters into glass-like shards, none of which match how marble actually breaks.
level_2: The marble fractures, but the exposed surface on the turned fragment looks smooth, shell-like (conchoidal), or made of flat repeating planes, more like a mineral with cleavage than marble's true crystalline-grain breakage.
level_3: The marble breaks into multiple pieces; the turned fragment's exposed face is rough and irregular rather than smooth or flat, but it is hard to tell whether that roughness comes from many small interlocking crystal grains or just from a jagged, uneven break, because the view is too brief, too dark, or too far away to judge clearly.
level_4: Everything at level 3 holds, and additionally: the exposed face clearly shows many small, differently angled crystal facets catching the light (a granular, sugary look) rather than one or a few large flat surfaces, even though dust, shadow, or brief framing makes some part of it hard to judge.
level_5: Everything at level 4 holds, and additionally: the exposed face is clearly and steadily visible enough to confirm it is made up of many small interlocking crystal grains across its whole surface, with no flat cleavage plane or smooth curved area anywhere on it, a texture clearly different from a smooth or planar break.

Spatiotemporal Consistency rubric:
level_1: The hammer or marble appears or disappears abruptly between frames; the marble jumps off the workbench before any impact is shown; a fragment spins in place with no hand or tool visibly holding it; the lighting suddenly flashes or goes dark with no motion to explain it; the workbench or a fragment's shape distorts abruptly between frames.
level_2: The marble sits still before impact, but the hammer's approach is jerky, skipping between positions rather than moving continuously; the lifted fragment starts rising before the fracture has actually finished; the turned fragment appears to rotate around a point in mid-air rather than around the hand or tool actually holding it.
level_3: The hammer, marble, and fragments all stay physically grounded throughout; the hammer moves continuously toward the marble and makes contact; the fracture spreads visibly across the marble; the separated fragments don't merge back together or pass through each other; one fragment lifts smoothly and begins turning, though its rotation axis or lift path shifts slightly partway through.
level_4: Everything at level 3 holds, and additionally: the hammer's approach, contact, and pull-back all look physically plausible; the fracture starts at the impact point and spreads outward; the fragments keep a consistent size and shape once separated; the lifted fragment turns around a single, steady pivot near the hand or tool holding it, without the rotation abruptly stopping partway or the lighting flickering during the turn.
level_5: Everything at level 4 holds, and additionally: the hammer's whole motion looks like one continuous, natural swing; the fracture appears as a single coherent event rather than a jump-cut; every fragment keeps a consistent size, shape, and orientation once it settles; the lifted fragment rises and then completes a full turn around one stable pivot point, staying visible and evenly lit the entire time with no interruption.