Ivory or Bone? Re-Examining a Late Qing Guanyin with New Macro Evidence

Material identification is sometimes less linear than a catalogue label suggests. An earlier examination of this monumental Late Qing Guanyin favoured carved bone: several close photographs appeared to show small pores and channel-like features, while the large composite construction seemed consistent with bone plaques assembled over a supporting structure.

Then more evidence arrived. New macro photographs showed unusually dense, compact material with few obvious open canals. A strong flashlight held against the carving did not merely illuminate the surface; light travelled through the wall and visibly illuminated material on the opposite side. A heated-needle test also failed to penetrate the surface. Most importantly, additional edge and internal photographs showed that the earlier assumption — a hollow section must mean bone — was too simple.

This follow-up records that re-examination. The purpose is not to force the object back into the category of ivory, but to ask a narrower and more useful question: what do the photographs and simple non-destructive observations actually prove, and where does visual identification stop?

Why the original bone attribution was plausible

Bone is one of the most common natural substitutes for ivory in Asian carvings. Compact bone is penetrated by vascular structures known as Haversian systems. On a polished worked surface, their canals may appear as small pits, dark pinpoints or short irregular streaks. When these are clearly and repeatedly visible, they are a strong diagnostic feature for bone rather than dentine.

Some of the first photographs of this Guanyin seemed to show exactly that kind of surface. Combined with the sculpture's sectional construction, the evidence initially supported a bone attribution.

The important correction is that not every dark point is a Haversian canal. A true identification should show a recurring anatomical pattern within the material itself. Once additional areas were examined, the expected field of obvious pores was much less convincing than it first appeared.

The new clue: unusually strong translucency

A strong flashlight was placed directly against the carving. Instead of producing only a bright spot at the point of contact, the material carried light through a much larger area. In thin sections, the opposite side could also be seen to glow.

That observation matters because dentine — the principal material of a tusk — can be strongly translucent when cut thin. Old polished ivory often produces a warm, diffuse glow under transmitted light. The effect can be striking enough that a carved section appears almost illuminated from within.

However, translucency is supporting evidence, not a species test. Dense cortical bone can also transmit light when it is sufficiently thin and polished. The flashlight observation therefore weakens an easy assumption of porous bone, but it cannot by itself prove elephant ivory.

Hardness: what the needle test can and cannot tell us

A heated needle was also tried on an inconspicuous area. It did not penetrate the material.

This is useful mainly because it argues against many soft plastics and thermoplastic imitations, which may melt, deform or accept a hot point. It is not a reliable bone-versus-ivory test. Both bone and ivory are highly mineralised biological materials dominated by hydroxyapatite and collagen-derived components. Both can resist a needle extremely well.

For valuable objects, destructive burn tests should not be repeated. Once synthetic resin has been reasonably excluded, microscopy and structural examination provide more useful information without damaging the object.

Where are the Haversian canals?

The later macro photographs are important because several exposed areas appear remarkably compact. Instead of an obvious constellation of pits, the surface shows fine linear structure, tool marks and a dense underlying matrix.

This does not mean that the absence of visible pores proves ivory. Bone is anisotropic: its structures look different depending on whether it is cut transversely, longitudinally or obliquely. Polishing, dirt and surface coatings can also obscure small canals. A photograph must therefore show the right anatomical plane before absence becomes meaningful.

What can now be said is narrower: the new photographs do not provide the clear Haversian-system evidence that would allow us to call the material bone with confidence.

The lines: Schreger pattern or something else?

Elephant and mammoth tusk dentine can display the characteristic intersecting pattern known as Schreger lines. On an appropriate transverse cross-section, these form opposing arcs or chevrons whose intersections create a cross-hatched or diamond-like pattern.

The familiar angle rule is useful only after a genuine outer Schreger pattern has first been identified. In practical identification guides, outer angles above roughly 115° support extant elephant ivory, angles below roughly 90° support mammoth ivory, while the intermediate range is not safely diagnostic on angle alone.

In the present photographs we see fine parallel and locally intersecting lines, but not yet a sufficiently broad, correctly oriented surface on which a Schreger pattern can be demonstrated beyond doubt. That distinction is critical. Measuring the angle of ordinary scratches or growth lines would create a precise-looking answer from the wrong structure.

Why a hollow section does not automatically prove bone

The largest change in the assessment concerns the internal cavity. Long bones contain a medullary cavity, so a hollow tube is naturally associated with bone. That is a useful first thought — but it is not exclusive to bone.

An elephant tusk is a modified incisor. Most of its mass is dentine, but the proximal part develops around a pulp cavity. Depending on where a tusk was cut and how a workshop used the material, a carved section can therefore include a substantial internal cavity. The mere existence of a void cannot decide between long bone and tusk.

This is precisely why the earlier statement “large central cavity equals bone” was too categorical. The shape, wall structure, anatomical orientation and relationship to the original raw material all matter.

What the rough edge contributes

Rough or broken edges are often more informative than polished display surfaces because they expose the internal material without a finish. In this object, the rough edge again appears compact and mineralised. We do not see a clearly trabecular, sponge-like transition in the photographed area.

Again, the evidence shifts probability rather than delivering an absolute identification. A useful material study is built from several independent features that agree with one another, not from whichever single test gives the preferred answer.

What the evidence supports now

Observation	Interpretation
Strong transmitted-light glow	Compatible with dense dentine/ivory; also possible in thin dense cortical bone.
Needle does not penetrate	Supports hard mineralised natural material and argues against many plastics; does not separate bone from ivory.
No convincing field of Haversian pits in later macro areas	Weakens the earlier bone attribution, but cut orientation can hide canals.
Dense compact edge structure	Consistent with dentine; also possible in cortical bone.
Internal cavity	Can occur in long bone as a medullary cavity and in the proximal part of a tusk as a pulp cavity.
No securely demonstrated Schreger field yet	Elephant or mammoth ivory is not yet visually proven from the photographs alone.

On balance, the additional evidence makes dentine/ivory a more serious — and in our present view, leading — hypothesis than the first examination allowed. At the same time, the photographs do not yet justify the stronger statement “confirmed elephant ivory.” That would require a diagnostic Schreger surface, a specialist anatomical examination or appropriate analytical testing.

What would settle the question?

The best next step is not another improvised household test. It is to obtain one of the following forms of evidence:

1. A correctly oriented transverse dentine surface. If a broad outer Schreger field can be documented clearly, proboscidean ivory can be identified visually and the outer-angle pattern can help distinguish extant elephant from mammoth.

2. Expert microscopy of a genuine exposed material plane. Repeated Haversian-system pitting would establish bone. A dense dentine microstructure without those canals would support ivory.

3. Laboratory spectroscopy. FTIR or Raman spectroscopy can distinguish many synthetic substitutes from hydroxyapatite-based natural materials and can contribute to ivory identification. Where species-level certainty is required, additional specialist methods may be necessary.

4. Imaging of the internal geometry. Radiography or CT can sometimes show whether the cavity and wall structure correspond more closely to a tusk or a long bone without cutting the object.

Why publishing the correction matters

Research is most useful when a conclusion is allowed to change. Our earlier article, When Ivory Was Bone, recorded the evidence available at that stage and explained why bone then seemed the stronger attribution. The later photographs and transmitted-light observations materially changed that balance.

That does not make the first examination worthless. It creates a research trail. The initial interpretation can be compared with the later evidence, and readers can see exactly which assumptions survived and which did not.

For collectors, dealers and researchers this is also a practical warning: colour, translucency, a hollow core, a needle test, one dark pore or one set of lines should never be used alone to certify ivory or bone. Material identification becomes reliable when independent anatomical features agree.

Current research status

The present working assessment is therefore deliberately precise:

The new macro and transmitted-light evidence weakens the earlier carved-bone attribution and currently favours dense dentine/ivory. Elephant ivory, however, is not yet confirmed from the available photographs because a diagnostic Schreger field has not been securely demonstrated.

If future examination establishes true Haversian-system pitting, the attribution should return to bone. If a correctly oriented outer Schreger pattern is documented, proboscidean ivory becomes demonstrable. Until then, the object remains an excellent example of why material research should record uncertainty rather than hide it.

For a standard visual reference to these diagnostic structures, see the CITES Identification Guide for Ivory and Ivory Substitutes.