What’s the difference between Goethite Brown Oxide (PY43) and Monte Amiata Natural Sienna (PBr7)?

Jane Blundell’s Ultimate Mixing Palette includes the highly granulating ochre Goethite Brown Oxide (PY43), with Monte Amiata Natural Sienna (PBr7) listed as an alternative. But what’s the difference between these two colors?

DS Goethite (PY43) vs. DS Monte Amiata Natural Sienna (PBr7) on Stilman & Birn Beta

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