pebble
Enable an agent to recognise a pebble, assess its physical condition and geological context, and judge suitable handling, study or use.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
recalled by Codex without web access - no source was read
Researched by: Codex
Purpose and description
Enable an agent to recognise a pebble, assess its physical condition and geological context, and judge suitable handling, study or use.
A pebble is a small rock fragment, commonly rounded in ordinary usage, classified in sedimentology as a gravel-sized clast between 4 and 64 millimetres in diameter on the Udden-Wentworth scale.
It can be Measure, weigh and photograph the pebble with scale and wetness documented.; Classify size, roundedness and form using declared conventions.; Inspect composition, coatings and fractures, escalating to material tests when justified.; Compare the specimen with neighbouring clasts to assess whether it is typical of its deposit.; Assess suitability for sorting, display, stacking or skipping from its shape and condition.; Collect, clean, sample or leave it in place according to site permissions and the evidence those actions could disturb..
Distinguishing features
Identify a discrete stone clast rather than a continuous exposure of bedrock or an aggregate of many grains.
Measure the clast using a declared grain-size convention before distinguishing pebble from granule or cobble in technical usage.
Record roundedness independently: a smooth surface alone does not establish a technical pebble classification.
Inspect material and fabrication evidence to distinguish a stone clast from a shell fragment, ceramic fragment or manufactured pellet.
Distinguish one pebble from gravel, which describes a collection or sediment size grouping rather than necessarily one clast.
Scope
+ Recognition of a discrete stone as a pebble under an explicitly named usage or classification
+ Specimen dimensions, shape, surface texture and material composition
+ Evidence of weathering, abrasion, fracture and transport
+ Occurrence as a loose clast or a distinguishable clast within a deposit
+ Suitability for collection, examination and small-scale practical use
- Bulk gravel deposits and their engineering performance
- Bedrock bodies and regional geological history
- Mineral species and rock types as independent kinds
- Artificial beads, pellets and manufactured stone products
- Pebble beaches, river channels and other landforms as whole systems
Characteristics
- Naming and classification basis
- Everyday usage; named sedimentological convention; unresolved The word can express an everyday judgement or a technical size class with different boundaries.
- Principal dimensions
- Longest, intermediate and shortest axes in mm, with method and uncertainty Dimensions support size classification and distinguish flat, elongate and equant specimens.
- Mass
- g, with dry or wet condition stated Mass informs handling and use and can support material assessment when combined with volume.
- Roundedness
- Named visual scale with reference images; unassessed Edge rounding helps describe abrasion without confusing it with overall shape.
- Overall form
- Equant; discoidal; bladed; elongate; irregular, under a stated method Form affects packing, rolling, stacking and suitability for uses such as skipping.
- Rock or mineral composition
- Observed or tested material identification, confidence and method; unknown Composition influences durability and interpretation of possible geological sources.
- Surface condition
- Observed roughness, polish, pits, coatings, staining and adhering sediment Surface features may affect handling and preserve evidence that cleaning could remove.
- Structural integrity
- Apparently intact; cracked; flaking; friable; freshly fractured; unassessed Condition governs whether manipulation or testing could fragment the specimen.
- Occurrence and collection context
- Observed location, host deposit, embedded or loose position, collection event and subsequent movements A pebble's present location is evidence of occurrence but does not necessarily identify its geological origin.
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 5 bundles · 9 layers · 15 findings · 23 questions.
Pebble recognition Establish the stone-clast sense and the basis for applying the name pebble.
Everyday naming and technical grain-size classification must remain distinguishable.
Stone clast boundary
Recognise an individual stone fragment and distinguish neighbouring object kinds.
Discrete stone identity
Record evidence for a discrete stone clast, including uncertainty about material and manufacture.
- What observations establish that this is one stone clast rather than bedrock, a composite aggregate or a non-stone fragment? boundary
- Do surface geometry, material or tool marks suggest manufacture or deliberate shaping? provenance
Size class boundary
Apply a declared meaning of pebble using reproducible measurements where needed.
Classification basis
Keep the naming convention, dimensional evidence and boundary uncertainty together.
- Is pebble being used as an everyday name or as a size class in a named sedimentological convention? definition
- Which dimension or sieve measurement determines the class, and could measurement uncertainty place the specimen in an adjacent class? measurement
Clast form and material Describe the geometry and substance that make this pebble physically distinctive.
Size alone cannot explain a pebble's behaviour or distinguish its composition and form.
Geometry and rounding
Separate whole-clast proportions from edge rounding and surface texture.
Measured clast form
Record principal axes, form and roundedness without using smoothness as a substitute for any of them.
- What are the longest, intermediate and shortest axes, and what form do their proportions support? measurement
- How rounded are the edges under a declared visual scale, independently of surface polish? measurement
Composition and fabric
Identify constituent material and internal features visible without unnecessary damage.
Material identification confidence
Separate directly observed grains, bands and inclusions from inferred rock or mineral identification.
- Which visible grains, bands, pores or inclusions support the proposed material identification? definition
- Which additional observation or test would distinguish the remaining candidate materials, and would it damage the pebble? action
Surface history and occurrence Record evidence of alteration and context while keeping geological explanations provisional.
A rounded pebble may have several possible histories, and its current setting need not be where it formed.
Abrasion, weathering and fracture
Describe surface features that may constrain the sequence of physical changes.
Surface evidence and alternatives
Document polish, pits, weathering rinds and fractures before assigning a process or environment.
- Which surfaces are rounded, polished, pitted, coated or freshly broken, and how do those features intersect? measurement
- What evidence distinguishes proposed water, ice, wind or artificial abrasion histories, and which alternatives remain plausible? provenance
Deposit and movement context
Connect the pebble to its observed setting and any documented relocation.
Occurrence versus origin
Record findspot and deposit relationships separately from hypotheses about source rock and transport.
- Was the pebble loose, embedded or deliberately placed, and what sediment or neighbouring clasts surrounded it? provenance
- What supports a proposed source area or transport history beyond the pebble's present location? provenance
Specimen condition and intervention Judge what can be done with the pebble while accounting for fragility and contextual evidence.
Cleaning, moving or striking a pebble can change both the specimen and the information available from it.
Integrity and use fit
Relate fractures, friability, form and mass to a specified use.
Use-specific suitability
Assess suitability for a named activity from observed properties rather than from the label pebble.
- Are there cracks, loose grains, flakes or sharp fracture edges that affect handling or likely breakage? measurement
- For the intended use, which requirements for mass, flatness, roundedness and durability does this pebble meet? action
Collection, cleaning and sampling
Select interventions with attention to collection authority and loss of geological or cultural evidence.
Evidence-preserving intervention
Determine whether moving, washing or sampling the pebble is justified and what must first be recorded.
- What site rules, ownership conditions or possible archaeological context govern removal or alteration of this pebble? action
- Which coatings, adhering sediments, marks or positional relationships would cleaning or collection destroy, and how should they be documented first? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- The sense assumed here is a natural rock fragment, not a product or proper name.
- Roundness is common but is not required by the sedimentological size classification.
- Size boundaries and diameter measurement conventions should be checked against the classification used by the intended application.
- Which of these check these first hold for the sense of pebble this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Quartz pebbles
- Flint pebbles
- Granite pebbles
- Limestone pebbles
- Which of these kinds and varieties hold for the sense of pebble this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Landscaping and decorative ground cover
- Aggregate for construction when material properties and grading are suitable
- Drainage layers
- Evidence for sediment transport, depositional environments and source geology
- Which of these real-world use hold for the sense of pebble this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- Particle diameter - 4-64; a classification interval on the Udden-Wentworth scale - mm
- Which of these typical measurements hold for the sense of pebble this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- Loose pebbles can create slipping or rolling hazards underfoot.
- Small pebbles can present a choking hazard.
- Pebbles ejected by tyres or machinery can cause impact injuries.
- Weathering and abrasion can fracture or wear pebbles, depending on their composition.
- Which of these failure modes and hazards hold for the sense of pebble this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- Everyday usage is less size-specific than sedimentological usage.
- Engineering soil classifications can use gravel size boundaries that differ from the Udden-Wentworth subdivisions.
- Which of these regional variation hold for the sense of pebble this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- gravel - Gravel is the broader sediment size category that includes pebbles; a pebble is an individual clast within it.
- granule - On the Udden-Wentworth scale, granules occupy the 2-4 mm interval immediately below pebbles.
- cobble - On the Udden-Wentworth scale, cobbles occupy the 64-256 mm interval immediately above pebbles.
- stone - Stone is a broader everyday term without a fixed particle-size interval.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of pebble this model covers, and on what evidence? provenance
What the second pass must settle
- Which everyday and technical senses should the registry explicitly admit, and which grain-size convention and boundary rules should govern technical classification?
- Should artificial tumbling or deliberate shaping leave a stone within this entry, or transfer ownership to a manufactured stone-product model?
- How should pebble-sized clasts embedded in consolidated rock relate to this model and to the host-rock model?
- Which roundedness and form assessment methods are sufficiently repeatable for agent use from photographs?
- Does an existing Vercy world model already own pebble or stone clast, requiring this registry entry to link to it?