INSTITUTE OF GEMSTONE & MINERAL RESEARCH • TECHNICAL SPECIFICATIONS

Statutory Crystal Grading Tier Specifications

The official grading criteria and quantitative thresholds for natural crystals, mineral specimens, and sagenitic gems. Defining unambiguous laboratory metrics: luminous transmittance tiers (τ at 550 nm), crystallographic termination integrity (T-0 to T-3), and 100-point 5R inclusion scoring under Article 6.0 circuit-breaker rules.

CUT CRYSTALS • 4C+1L

CCGS Clarity (5 Tiers)

Quantitative grading of faceted gems and commercial beads based on spectrophotometric luminous transmittance (τ) at 550 nm:

• EC (≥92%): Extra Clean, eye-clean optical glass purity.
• VSC (85-91%): Very Slight Cloud, microscopic dust veil.
• SC (75-84%): Slight Cloud, visible fluid inclusions.
• MC (60-74%): Moderate Cloud, partial translucency.
• OP (<60%): Opaque, structural light extinction.

NATURAL MINERALS • 5R

MSGS Termination (4 Tiers)

3D optical profilometry measurement of defect area ratios across natural crystal tips, prism facets, and cleavage planes:

• T-0 (0% Defect): Pristine natural termination apex.
• T-1 (<3% Area): Minor contact micro-nibbles ≤1mm.
• T-2 (3-10% Area): Cleavage chips, natural healed impact.
• T-3 (Repaired): Mechanical repair, regrinding or resin join.

RUTILATED • 4M SYSTEM

RCGS Scoring (4 Tiers)

100-point physical evaluation combining Density, Chatoyancy, Host Purity, Root Balance, and Metallic Luster:

• Tier 1 / EX (95-100 Pts): Museum & holotype standard.
• Tier 2 / VG (85-94 Pts): High collector benchmark.
• Tier 3 / G (75-84 Pts): Commercial grade ([RC] hard cap).
• Tier 4 / ST (60-74 Pts): Mass-market decorative grade.

EMPIRICAL TRANSMITTANCE MATRIX

CCGS Commercial Crystal Clarity Grade Thresholds

TIER CODE	DESIGNATION	TRANSMITTANCE (τ 550nm)	INTERNAL INCLUSION CHARACTERISTICS	MARKET CLASS
EC	Extra Clean	τ ≥ 92.0%	Optically flawless under 10x darkfield magnification. Complete absence of fluid veils, two-phase inclusions, fractures, and cloudiness.	Investment Gem
VSC	Very Slight Cloud	85.0% ≤ τ < 92.0%	Eye-clean from 25 cm distance. Isolated sub-micron pinpoint inclusions visible under 10x magnification without affecting overall body transparency.	Fine Jewelry
SC	Slight Cloud	75.0% ≤ τ < 85.0%	Localized fluid veils, healed cleavage fissures, or minor negative crystal groups visible to the unaided eye. Transmittance remains bright.	Commercial Gem
MC	Moderate Cloud	60.0% ≤ τ < 75.0%	Dispersed micro-droplets, milky hydrothermal clouds, or dense internal fracturing causing noticeable haziness across ≥30% of the crystal volume.	Standard Bead
OP	Opaque	τ < 60.0%	Complete or near-complete light extinction. Severe internal turbidity or mineral mass inclusions rendering the quartz translucent to opaque.	Carving Grade

TERMINATION INTEGRITY • 5R INCLUSION VECTORS

MSGS & RCGS Detailed Grade Specifications

MSGS Natural Mineral Specimen Ratings

Governed by 3D optical profilometry of crystal apex faces: T-0 represents pristine growth faces with zero mechanical impact. T-1 permits microscopic chipping (<3% defect area, ≤1 mm). T-2 marks pronounced cleavage damage (3–10% defect area). T-3 designates specimens subjected to mechanical tip repairs, artificial face repolishing, or epoxy joins.

RCGS 5R Scoring & Article 6.0 Ceiling Cap

Calculated across five weighted vectors totaling 100 points: Needle Density (R1, max 25), Chatoyancy Alignment (R2, max 25), Host Glass Purity (R3, max 20), Root Equilibrium (R4, max 15), and Luster (R5, max 15).

Article 6.0 Mandatory Ceiling:
Detection of polymer resin infill (Micro-FTIR 3054 cm⁻¹ peak) enforces an unalterable hard ceiling at Tier 3 / G (Max 84 Pts), permanently barring the specimen from Tier 1 (EX) or Tier 2 (VG) collector classifications.